The correct answer is "My best friends are Sarah Katie and Mike." This is the correct choice because it contains an error in punctuation: when writing a list, each item needs to be separated by a comma, so there should be commas after the names Sarah and Katie. Each of the other sentences is correctly punctuated.

The correct answer is "Elephants my favorite animals are in danger of extinction." This sentence is incorrectly punctuated because the phrase "my favorite animals" is a non-essential clause that appears in the middle of the sentence, so it needs to be set off with two commas. Since there are no commas in the sentence, it is incorrect. The other sentences are all punctuated correctly.

The correct answer is "Harry please come look at this immediately!" This sentence is incorrect because it lacks a comma after the name, Harry. Since the speaker is addressing him, his name needs to be set off from the rest of the sentence with a comma.

The correct answer is No error because "its" is the possessive form of it, and here we are talking about the cover of the book, and so it is correct to use "its" in the possessive sense. When used with an apostrophe, the word "it's" is a contraction meaning "it is" or "it has." This sentence is not trying to say it is or it has, and so the best choice is no error.

The correct answer is "I waited in line, gave my tickets to the agent, and boarded the plane." This is because since we have a list of three items, we need to separate each item with a comma. One comma is incorrect, as is no commas. Leaving out the commas leads to confusion.

The correct answer is "The team's victory was well-deserved." A team is a singular noun, and when it shows possession it requires an apostrophe s. The word "teams" without an apostrophe means multiple teams, which this sentence does not communicate. The word "teams's" is the possessive form of multiple teams. There should not be a comma in the middle of this sentence since it is a simple sentence with one independent clause and no dependent clauses or modifiers.

The correct answer is "William, my oldest cousin, is getting married in October." This sentence correctly punctuates the phrase "my oldest cousin," setting it apart with two commas, as is required when placing non-essential clauses in the middle of a sentence. One or no commas is incorrect, which is why "William, my oldest cousin, is getting married in October" is the only correct answer.

The correct answer is "In 1929, the year the stock market crashed, many people lost their jobs." This is correct because it sets off the non-essential clause "the year the stock market crashed" with commas. Since the sentence would still make sense without this information, it is considered non-essential, and always enclosed in commas when it occurs in the middle of a sentence. It is incorrect to omit one or both commas; both are necessary.

The correct answer is, "When I was in second grade I broke my arm." This sentence is incorrectly punctuated because it lacks a comma after the word grade. When a sentence begins with a dependent clause, such as "when I was in second grade," it requires a comma to set it apart from the independent clause. If the dependent clause comes second in the sentence, it does not require a comma. The other choices are correctly punctuated.

The correct answer is "Mary stop hitting your brother." This sentence is contains an error in punctuation because the name Mary needs to be followed by a comma. Whenever someone is being directly addressed, and their name is used, the writer needs to separate the name with a comma. The other answer choices are correctly punctuated.