If a castle wall or a defense is “vulnerable,” it is open to an attack or lacking a defense. It is similar in meaning to "undefended," which means not defended. To further help you, if you are “reckless,” you do not consider the results of your actions; “frightened” means scared.

"Analyze" means to study closely, so "study" is the correct answer. None of the other answer choices are close in meaning to "study": "ignore" means refuse to pay any attention to; "mock" means make fun of; "decide" means choose; and "test," when used as a verb, means evaluate or investigate.

"Topple" means to fall or to cause to fall and can be used in a literal, physical sense, like "The tree the lumberjack had been chopping at for an hour finally toppled over," or it can be used in a metaphorical sense, like "The prejudiced government was toppled and a new, more egalitarian one was established in its place." So, "overthrow," which means unseat from a role of power through the use of force, is the correct answer, as it is close in meaning to the second described meaning of "topple."

"Normal" is defined as conforming to a usual standard. Since "ordinary" is defined as normal or not distinct, "ordinary" is our best answer choice. "Abnormal" and "normal" are antonyms.

To "destroy" something means to dismantle it completely, or to demolish it, so "demolish" is the correct answer. Considering the answer choices, "employ" means make use of, a "convoy" is a groups of vehicles traveling together, to "abolish" something means to put an end to it, and "create" means make, produce,or generate.

The prefix "semi-" usually means half, so we can assume that a “semicircle” is half a circle. To provide further help, a three-dimensional circle is called a “sphere;” “parallel” means running alongside, having the same slope; “slope” means slanted ground; “gradient” means slope. In addition to being terms we use in English, these are also all mathematical terms.

The noun "change" is closest in meaning to "alteration." These words are synonymous. All of the other answer choices are a) not related to the word "change" and b) closely related to each other. If you recognize all of the answer choices that mean nearly the same thing to each other, you can easily find the answer choice that stands out as being unrelated to the other incorrect choices.

"Accurate" means correctly measured, exact, or precise, so "exact" is the correct answer. To help you, "imprecise" means not accurate, and "timely" means occurring at the right time.

VITAL means significant or important.

"Illumination" comes from the root verb "illuminate" which means to light something up. The suffix "-ion" indicates a noun.