Spanish 2 Quiz: Preterite Iy Patterns

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Preterite Iy PatternsQuestion 1 of 10

A language learner studying Spanish verb patterns notices that the verb huir (to flee) produces "huyó" (3sg preterite) and "huyeron" (3pl preterite), and wonders whether this is the same i→y rule seen in leer (leyó) and oír (oyó).

Which analysis of the learner's observation is most linguistically accurate?

The learner is correct that all three verbs follow the same rule: whenever a preterite ending beginning with -i- is added to any verb whose infinitive contains the letter -u-, the -i- automatically becomes -y- to prevent a two-vowel cluster in the written form.

The learner is incorrect: "huyó" and "huyeron" are errors; the correct preterite forms of huir are "huió" and "huieron," following the same logic as other -ir verbs. The -y- forms are colloquial variants not accepted in standard written Spanish.

The learner is partially correct: "huyó" looks similar to "leyó" and "oyó," but the -y- in huir's conjugations comes from a different source — the -uir verb group inserts -y- throughout the present tense and in 3rd-person preterite forms as part of the verb's stem pattern, whereas in leer and oír the -y- is a reactive spelling fix for an unstressed intervocalic -i-.

The learner is incorrect because the i→y rule applies only to -er verbs (like leer and creer) and never to -ir or -uir verbs; "huyó" must therefore be explained by a completely unrelated irregular conjugation pattern unique to the verb huir.

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Spanish 2 Quiz

Spanish 2 Quiz: Preterite Iy Patterns

Practice Preterite Iy Patterns in Spanish 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Preterite Iy Patterns, giving you a quick way to practice the rules, question types, and explanations that matter most for Spanish 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Which analysis of the learner's observation is most linguistically accurate?

The learner is correct that all three verbs follow the same rule: whenever a preterite ending beginning with -i- is added to any verb whose infinitive contains the letter -u-, the -i- automatically becomes -y- to prevent a two-vowel cluster in the written form.
The learner is incorrect: "huyó" and "huyeron" are errors; the correct preterite forms of huir are "huió" and "huieron," following the same logic as other -ir verbs. The -y- forms are colloquial variants not accepted in standard written Spanish.
The learner is partially correct: "huyó" looks similar to "leyó" and "oyó," but the -y- in huir's conjugations comes from a different source — the -uir verb group inserts -y- throughout the present tense and in 3rd-person preterite forms as part of the verb's stem pattern, whereas in leer and oír the -y- is a reactive spelling fix for an unstressed intervocalic -i-. (correct answer)
The learner is incorrect because the i→y rule applies only to -er verbs (like leer and creer) and never to -ir or -uir verbs; "huyó" must therefore be explained by a completely unrelated irregular conjugation pattern unique to the verb huir.

Explanation: When you see questions comparing verb spelling changes across different verb classes, your job is to ask why the change happens — not just that it happens. Surface-level similarity can mask completely different underlying mechanisms. In Spanish, two distinct processes produce a written -y-. For verbs like leer and oír, the -y- is a reactive spelling adjustment: when an unstressed -i- falls between two vowels (le-i-ó → leyó), Spanish orthography converts it to -y- because an unstressed intervocalic -i- is considered non-standard in writing. The -y- isn't part of the verb's stem — it's a fix applied at the boundary. For -uir verbs like huir, the situation is different. The -y- is a built-in stem feature: it appears throughout the present tense (huyo, huyes, huye, huyen) and carries into the 3rd-person preterite (huyó, huyeron). This makes C the most accurate answer — the learner spots a real pattern but misidentifies it as the same rule. Choice A is wrong because it invents an overly broad rule tied to the letter -u- in the infinitive, which doesn't exist. Many -u- verbs (like subir) show no such change. Choice B is flatly incorrect — "huió" and "huieron" are not valid forms; the -y- conjugations of huir are standard and required. Choice D is wrong because it falsely restricts the i→y spelling fix to -er verbs; oír is an -ir verb and follows the same reactive rule as leer. Your study tip: always ask whether a spelling change is stem-driven (part of the verb's pattern throughout conjugation) or boundary-reactive (triggered only when vowels collide at a suffix seam). That distinction separates real mastery from surface-level pattern matching.

Question 2

A Spanish instructor explains: "The i→y change in the preterite is an orthographic rule, not a phonological irregularity." Which of the following statements best supports this claim by accurately describing the rule's scope and motivation?

The change is orthographic because it applies exclusively to irregular verbs in the preterite; marking irregularity in spelling without changing pronunciation is precisely what distinguishes an orthographic rule from a phonological one
The change is orthographic because it affects only the 3rd-person forms of the preterite, standardizing the written endings of -er and -ir verbs across those two persons without altering any sounds, which is the defining feature of a purely orthographic rule
The change is orthographic because it only affects how the verb is written, not how it is pronounced — the underlying sound /j/ (as in English 'yes') would exist whether written as -i- or -y-, and Spanish spelling conventions require -y- when this glide appears between two vowels in an unstressed position (correct answer)
The change is orthographic because Spanish orthography requires a written accent mark whenever an unstressed -i- appears next to another vowel, and writing -y- instead of -í- is an alternative way of satisfying this accent-placement requirement in the affected third-person forms

Explanation: When a question asks you to distinguish orthographic from phonological rules, focus on the key question: does the rule change how something sounds, or only how it's written? In the preterite, verbs like leer or caer produce forms like leyó and cayó instead of the expected *leió or *caió. The instructor's claim is that this spelling shift doesn't represent a new sound — the glide /j/ (like the "y" in English yes) is already present in the pronunciation regardless of spelling. Spanish orthographic convention simply requires that when this glide appears between two vowels in an unstressed syllable, it must be written as -y- rather than -i-. The sound stays the same; only the letter changes. That's exactly what option C captures: the underlying sound /j/ exists either way, and the -y- spelling is just the conventional representation of that sound in this phonetic environment. C is correct. Option A is wrong because it misidentifies the trigger — the change isn't exclusive to irregular verbs, and calling something orthographic doesn't hinge on irregularity. Option B contains a true fact (it does affect 3rd-person forms) but gives a faulty reason: simply "standardizing endings" doesn't define an orthographic rule — the motivation is the phonetic environment (glide between vowels), not person-agreement patterns. Option D confuses two separate issues: accent marks (written accents like í) exist to mark stress, while the i→y change is about representing a glide consonant between vowels — these are distinct orthographic principles. Study tip: When you see "orthographic vs. phonological," always ask yourself: does the pronunciation actually change? If not, the rule is orthographic by definition.

Question 3

Read the following paragraph from a student's composition:

"El sábado pasado, mis amigos y yo fuimos al parque. Yo (1) música en mi teléfono mientras mi amigo Carlos (2) un artículo largo sobre historia. Después, todos nosotros (3) un podcast interesante sobre ciencias."

Which set of forms correctly fills blanks (1), (2), and (3) with the preterite of oír, leer, and oír respectively?

(1) oí, (2) leyó, (3) oímos — because the i→y change applies only to third-person forms, leaving first-person singular "oí" and first-person plural "oímos" with their standard stressed accented endings intact. (correct answer)
(1) oyí, (2) leyó, (3) oyimos — because the i→y change applies to all persons of oír in the preterite, converting every unstressed -i- to -y- regardless of whether the vowel carries a written accent.
(1) oí, (2) leyió, (3) oímos — because leer requires the full -ió ending in third-person singular without modification, while oír takes the standard -í and -ímos endings throughout the paradigm.
(1) oyó, (2) leyó, (3) oyeron — because the subject pronouns "yo" and "nosotros" are optional in Spanish, so any third-person form is equally acceptable when the subject is clearly implied by context.

Explanation: When working with preterite spelling-change verbs like oír and leer, the key question to ask yourself is: which persons trigger the i→y change, and which ones simply need a written accent? Both verbs belong to a group where an unstressed -i- between two vowels becomes -y- — but this only happens in the third-person forms (él/ella and ellos/ellas): leyó, leyeron, oyó, oyeron. In all other persons, the -i- stays but must carry a written accent to show it's a strong, stressed vowel: oí, oíste, oímos; leí, leíste, leímos. Answer A is correct because it applies this rule precisely. Blank (1) is yo → oí ✓, blank (2) is él (Carlos) → leyó ✓, and blank (3) is nosotros → oímos ✓. The accents on oí and oímos prevent those vowels from blending into a diphthong, preserving the correct pronunciation. Answer B is wrong because it wrongly extends the i→y change to every person, producing invented forms like oyí and oyimos that don't exist in Spanish. Answer C is wrong because it invents leyió — a non-existent form. The third-person singular of leer is leyó (the -i- converts to -y- and the remaining -ó carries the accent), not leyió. Answer D is wrong on two levels: it uses third-person forms (oyó, oyeron) for first-person subjects, and its justification — that implied subjects allow any person — is grammatically false in Spanish. Study tip: Memorize that the i→y swap in oír and leer is only third-person. For all other forms, keep the -i- and add a written accent.

Question 4

Marta le escribe un mensaje a su amiga: "Ayer me quedé en casa todo el día. Puse música y un libro entero de poesía. ¡Fue un día increíble!"

Which form correctly completes Marta's message, and why is this verb affected by the i→y spelling change in the preterite?

leí — the first-person singular preterite of leer ends in -í; the i→y change does not apply here because the -í is stressed, so no unstressed intervocalic -i- is produced (correct answer)
leyí — the i→y change applies to the first-person singular when the stem ends in a vowel, turning the -í ending into -yí to avoid a triple vowel cluster in the written form
leyó — the i→y change is required for leer, but it only produces the third-person singular form; the first-person singular is a completely separate, irregular form that must be looked up individually
leío — an unstressed -i- between two vowels shifts to -o- in the first person to match the stem vowel pattern of leer and similar two-vowel stem verbs

Explanation: When working with preterite spelling changes, the key question to ask is: does an unstressed -i- end up between two vowels? If yes, that -i- shifts to -y-. If no, regular spelling rules apply. For leer, the stem ends in -e (a vowel). When you add preterite endings, you need to check each form. The third-person forms — leyó and leyeron — are where the change triggers, because the -i- of the ending would land between the stem vowel -e- and another vowel, creating an awkward unstressed intervocalic -i-. Spanish resolves this by writing -y- instead. But the first-person singular ending is -í, which is stressed. A stressed -í- is never converted to -y-, because the rule targets only unstressed intervocalic -i-. So leí stands as written — no spelling change needed. That makes A the correct answer and the correct completion of Marta's message. Choice B (leyí) incorrectly applies the y-change to the first person, inventing a form that doesn't exist. The stress on the -í ending is precisely what blocks the change. Choice C (leyó) confuses the third-person singular form (which does require the change) with the first-person form Marta needs — these are different slots in the conjugation table. Choice D (leío) is simply fabricated; Spanish has no rule that shifts -i- to -o-. Your study tip: memorize that the i→y change in leer, creer, and oír affects only the third-person singular and plural (leyó, leyeron) — the forms where the -i- is unstressed and caught between vowels. First person (leí, creí, oí) stays clean.

Question 5

Which of the following verbs would NOT undergo the i→y spelling change in its preterite third-person singular form, and what is the key reason that distinguishes it from verbs that do?

Construir (to build) → construyó — the -y- in this form is part of the verb's inherent -uir stem pattern, not a reactive spelling adjustment triggered by an unstressed -i- falling between two vowels, as in leer or creer (correct answer)
Creer (to believe) → creyó — the -ee- stem absorbs the preterite ending without any modification, so the -y- insertion is unnecessary in the third-person singular; standard -er verb endings apply throughout
Leer (to read) → leyó — verbs with two consecutive vowels in the stem are exempt from the i→y rule, which is restricted to -ir verbs whose stems end in a single consonant followed by a vowel
Oír (to hear) → oyó — because oír carries an accent mark in the infinitive, it follows a separate conjugation pattern that replaces the standard preterite ending entirely rather than modifying the intervocalic -i-

Explanation: When studying preterite spelling changes, it helps to ask why the change happens before memorizing which verbs follow the rule. The i→y shift occurs when an unstressed -i- ends up sandwiched between two vowel sounds — the intervocalic environment forces the -i- to become -y- for pronunciation clarity. This is what happens with leer (le-ió → leyó) and oír (o-ió → oyó). Answer A is correct because construir tells a fundamentally different story. The -y- in construyó isn't a reactive spelling patch — it's a structural feature baked into all -uir verbs across multiple tenses and persons. The stem itself triggers -y- insertion as part of its regular conjugation pattern, not because an unstressed -i- fell between vowels in the preterite ending. That distinction is the heart of the question. Answer B is wrong because it claims creer doesn't need the -y- insertion — but creyó is the correct preterite form precisely because the unstressed -i- does fall between two vowels (the stem's final -e- and the ending's -ó), making the change mandatory, not unnecessary. Answer C is wrong because it inverts the rule entirely. The i→y change actually applies to verbs whose stems end in a vowel (creating the intervocalic trap), not to -ir verbs ending in a consonant. Leer undergoes the change; it is not exempt. Answer D is wrong because the accent mark on oír signals irregular stress in the infinitive but doesn't create an entirely separate conjugation logic — oyó still results from the standard intervocalic i→y adjustment. Study tip: Always ask whether the -y- in a verb form is structural (built into the stem pattern) or reactive (triggered by the intervocalic environment). That distinction separates -uir verbs from true i→y spelling-change verbs.

Question 6

Two students debate the preterite of creer:

Student A: "The 'ellos' form should be 'creyeron' because of the i→y rule." Student B: "No, it should be 'creieron' because -er verbs take -ieron in the preterite third-person plural, and creer is regular."

Which student is correct, and which linguistic principle most precisely explains the outcome?

Student B is correct. Creer is a regular -er verb, and its third-person plural preterite follows the standard pattern: cre- + ieron = creieron. The i→y rule is restricted to -ir verbs; it does not apply to -er verbs like creer, regardless of whether the stem ends in a vowel.
Student A is correct. Creer's stem ends in the vowel -e-, and adding the standard -ieron ending would produce creieron, in which an unstressed -i- falls between two vowels. Spanish orthography requires this unstressed intervocalic -i- to be written as -y-, yielding creyeron. This rule applies to both -er and -ir verbs with vowel-ending stems. (correct answer)
Student A is correct, but for a different reason: creer is a stem-changing verb in the preterite (e→y), analogous to the e→i shift in verbs like pedir. The -y- in creyeron reflects this stem alternation rather than a spelling convention about intervocalic vowels.
Both students are partially correct. The form creieron is acceptable in informal written Spanish, while creyeron is preferred in formal registers. The i→y rule functions as a stylistic guideline rather than a mandatory orthographic requirement in contemporary standard Spanish.

Explanation: When you encounter preterite forms of verbs whose stems end in a vowel, you need to think about Spanish's orthographic rules for intervocalic vowels — not just the standard conjugation endings. Creer is indeed an -er verb, and its preterite third-person plural ending is -ieron. The stem of creer is cre- (ending in the vowel e). Attaching -ieron produces cre + ieron = creieron, where an unstressed -i- sits between two other vowels (e...o). Spanish does not permit an unstressed -i- in this intervocalic position; the language requires it to be written — and pronounced — as -y-. The result is creyeron. This orthographic rule is not limited to -ir verbs; it applies to any verb whose stem ends in a vowel, including -er verbs like creer, leer, and proveer. Student A is correct, and answer B captures this precisely. Answer A is wrong because it confidently labels creer "regular" and claims creieron is valid — but creieron violates a mandatory Spanish spelling rule, not merely a stylistic preference. The form simply does not exist in standard Spanish. Answer C misidentifies the mechanism. Creer is not a stem-changing verb the way pedir (e→i) is. The -y- in creyeron is a spelling adjustment for an unstressed intervocalic -i-, not a stem alternation driven by verb class. Answer D is wrong because creyeron vs. creieron is not a formal/informal register distinction — creieron is always incorrect, in any context. Study tip: When conjugating verbs like creer or leer, always check: does the stem end in a vowel? If so, -ió becomes -yó and -ieron becomes -yeron — no exceptions.

Question 7

A student is conjugating caer (to fall) in the preterite and produces the following paradigm:

Person	Form written by student
yo	caí
tú	caíste
él/ella	cayó
nosotros	caímos
vosotros	caísteis
ellos	cayeron

The student's paradigm for caer in the preterite is evaluated by the instructor. Which conclusion is most accurate?

The paradigm is entirely incorrect because caer is an irregular verb that does not follow the i→y pattern; all forms should use the standard -er preterite endings without any -y- insertion or accent marks on the -i-.
The paradigm is correct throughout. Caer follows the same i→y pattern as leer and creer: 3sg and 3pl take the -y- form (cayó, cayeron) because an unstressed -i- would otherwise fall between two vowels, while all other forms retain the stressed -í- with a written accent. (correct answer)
The paradigm is partially correct: "cayó" and "cayeron" are right, but "caí," "caíste," "caímos," and "caísteis" should be written without accent marks since the -i- in these forms is unstressed and does not require orthographic marking.
The paradigm is partially correct: the 3sg and 3pl forms are right, but the 1sg should be "cayí" and the 2sg should be "cayíste" because caer's stem ends in a vowel, triggering the i→y change across all preterite forms that contain the letter -i-.

Explanation: When conjugating -er and -ir verbs whose stems end in a vowel — like leer, creer, and caer — Spanish applies a spelling rule to avoid an awkward, unstressed -i- squeezed between two other vowels. In those positions (third-person singular and plural of the preterite), the -i- shifts to -y-, giving you cayó and cayeron instead of the unacceptable *caió/*caieron. In all other preterite forms, however, the -i- is stressed and therefore stays as -í- with a written accent mark — that accent is not decorative; it signals that the i carries the syllable stress and functions as its own vowel rather than blending into a diphthong. This makes B the correct answer. The student's full paradigm is accurate: caí, caíste, caímos, caísteis correctly retain the accented -í-, and cayó, cayeron correctly apply the i→y shift. A is wrong because it denies that caer follows this well-established spelling pattern — the y-insertion and accent marks are both required and correct. C contains a critical error: it claims the -í- in forms like caí and caíste is unstressed and needs no accent. In reality, those -í- forms ARE stressed on the i, and without the accent mark they would be misspelled. D misapplies the rule by suggesting cayí or cayíste — the i→y change only occurs when the -i- would otherwise sit between two vowels, which is not the case in those forms. A handy memory trick: if you see vowel + i + vowel, the i becomes y. Otherwise, keep your -í- and accent it.

Question 8

A student wants to say "They heard the announcement and read the notice." She writes: "Ellos oyeron el anuncio y leyeron el aviso." Her classmate insists both verbs are wrong because neither follows normal -er preterite endings. Which response best evaluates the student's sentence?

The sentence is incorrect because "oyeron" should be "oieron" and "leyeron" should be "leieron" — the standard third-person plural preterite endings for -er verbs do not include y.
The sentence is correct. Both verbs undergo the i→y change in the third-person plural because an unstressed -i- would otherwise appear between two vowels, which is not permitted in standard Spanish orthography. (correct answer)
The sentence is partially correct. "Leyeron" is right because leer is irregular, but "oyeron" should be "oieron" because oír follows a different conjugation pattern that does not trigger the spelling change.
The sentence is incorrect because both verbs should be "oyaron" and "leyaron" — the -ar preterite endings apply when the stem ends in a vowel to avoid awkward vowel combinations in the third-person plural.

Explanation: Whenever you encounter preterite conjugations of verbs whose stems end in a vowel — like leer (le-) or oír (o-) — you need to think about a key phonological rule in Spanish: an unstressed i cannot stand between two vowels. Instead, it must shift to y. This is what drives the spelling change in certain preterite forms. Answer B is correct because both oyeron and leyeron follow this exact pattern. In the third-person plural preterite, the standard -er/-ir ending would produce -ieron. For leer, that gives le + ieron → leieron, but the unstressed i is sandwiched between two vowels, which violates Spanish orthographic rules. Spanish resolves this by converting that i to y: leyeron. The same logic applies to oír: o + ieron → oieron → oyeron. Both forms are grammatically and orthographically correct, making the original student's sentence perfectly fine. Answer A is wrong because it assumes the standard preterite endings should appear unchanged, ignoring the vowel-between-vowels rule that forces the i→y shift. Answer C contains a dangerous half-truth — it correctly validates leyeron but incorrectly rejects oyeron, treating the two verbs as if they follow different rules when in fact both undergo the identical spelling adjustment for the same reason. Answer D is entirely fabricated; Spanish never switches to -ar endings simply because a stem ends in a vowel — that's not a rule that exists anywhere in Spanish grammar. A helpful tip: whenever a verb's stem ends in a vowel, flag the third-person singular (ó→yó) and plural (ieron→yeron) preterite forms as likely candidates for this i→y shift.

Question 9

Profesor's quiz question: "Choose the sentence in which ALL preterite verb forms are spelled correctly."

I. Ella leyó el periódico y luego lo distribuyó.

II. Él oió las noticias y creyó todo lo que escuchó.

III. Nosotros leímos el informe y oímos la grabación.

IV. Ellos creyeron el rumor y lo releyeron dos veces.

Which sentence(s) contain ONLY correctly spelled preterite forms?

Sentences I and IV only, because "leyó," "distribuyó," "creyeron," and "releyeron" all correctly apply the i→y rule or standard conjugation patterns, while sentences II and III contain at least one error.
Sentences III and IV only, because first-person plural forms like "leímos" and "oímos" are always correct, and third-person plural i→y forms are handled properly in sentence IV.
Sentence I only, because "leyó" is correct but "distribuyó" does not follow the i→y rule and should be "distribuyió," making all other sentences also flawed.
Sentences I, III, and IV only, because "oió" in sentence II is incorrect — it should be "oyó" — while all verb forms in the other three sentences follow correct preterite spelling conventions. (correct answer)

Explanation: When conjugating -er and -ir verbs whose stems end in a vowel (like leer, oír, creer, distribuir) in the preterite, Spanish applies the i→y spelling rule: an unstressed i between two vowels becomes y. So leer → leyó, creer → creyó, distribuir → distribuyó, and critically, oír → oyó (not oió). The stem of oír is o-, so the intervening vowel becomes y, giving you oyó, oyeron, etc. Sentence II contains "oió" — this is the critical error. The correct form is oyó, making Sentence II the only one with a misspelling. Sentences I, III, and IV all contain valid preterite forms: leyó and distribuyó (Sentence I) correctly apply the i→y rule; leímos and oímos (Sentence III) are correct first-person plural forms where the accent mark preserves the strong vowel; creyeron and releyeron (Sentence IV) correctly apply the rule in the third-person plural. This confirms D as the answer. Choice A incorrectly claims Sentence III has an error — leímos and oímos are perfectly correct. Choice B wrongly excludes Sentence I, which contains no errors at all. Choice C misidentifies distribuyó as wrong — since distribuir ends in a vowel, the i→y conversion is exactly right. Study tip: For any verb whose infinitive ends in -uir or whose stem ends in a vowel, mentally check every preterite third-person form — these are the most tested spots for the i→y spelling rule.

Question 10

A student reviews four sentences and their evaluations below. Which evaluation correctly identifies whether an i→y preterite error is present?

"Mis padres no creyeron mi explicación cuando llegué tarde a casa." — The form creyeron is incorrect; it should be creieron because the i→y change does not apply when the stem already ends in the vowel -e-.
"El estudiante leyó el capítulo dos veces antes del examen." — The form leyó is incorrect; it should be leió because the standard third-person singular preterite ending -ió attaches directly to the stem without modification.
"Cuando oyeron la alarma, todos salieron corriendo del edificio." — The form oyeron is incorrect; it should be oieron because oír, as an irregular verb, takes standard preterite endings that do not trigger the i→y spelling adjustment.
"Ella leyó la carta, la dobló, y se la guardó en el bolsillo." — All preterite forms are correct: leyó properly applies the i→y change for leer in the third-person singular, while dobló and guardó follow standard -ar preterite patterns. (correct answer)

Explanation: Whenever you see a question about preterite spelling changes, focus on one key rule: verbs whose stems end in a vowel (like leer → le-, oír → o-, creer → cre-) require the i→y change in the third-person singular (leyó, oyó, creyó) and plural (leyeron, oyeron, creyeron) forms. This happens because Spanish does not allow an unstressed i squeezed between two vowels — it automatically becomes y for pronunciation clarity. Option D is correct because every verb in the sentence is handled properly. Leyó correctly applies the i→y rule (not leió), while dobló and guardó are standard -ar preterite forms that need no adjustment since their stems end in consonants, not vowels. The evaluation in D accurately describes all three forms. Option A is wrong because it claims creyeron should be creieron — but that's exactly the scenario where the rule does apply. The stem cre- ends in the vowel e, so the unstressed i must become y, giving you creyeron, which is already correct. Option B makes the same type of error in reverse: it claims leyó is wrong and should be leió, but leió would violate the very rule being tested. The stem le- ends in a vowel, so leyó is the required correct form. Option C incorrectly argues that oír's irregularity somehow exempts it from the i→y change — it doesn't. Oyeron is the correct preterite form, not oieron. As a study tip, remember: vowel stem + preterite i = always becomes y. No exceptions among this verb group.