这个词的前提”,“一个复数pronoun, is the word "mom," a singular noun. Pronouns need to match their antecedents' gender and number, so the singular feminine pronoun "her" should be used instead of the plural pronoun "them."

Given that the subject of the sentence is "New York and Los Angeles," which is plural, the pronoun "its" should also be plural. Therefore, "its" should be "their."

"Their" is a possessive pronoun that indicates that someone belongs to several people. This sentence, however, refers to a single subject (a professor), so the best pronoun to use is one that signifies that an object belongs to one person: in this case, his students. Even though "students" is plural, the plurality of the object does not impact the possessive pronoun. Only the plurality of the subject matters, so "his" is the correct pronoun, making the corrected sentence "A professor who assigns an unreasonable amount of reading for his students may never earn the class's approval."

In this sentence, the pronoun “it” (singular) refers to “witty comebacks” (plural). These words should agree in number. The corrected sentence reads, "Penelope always thought of the most fabulous witty comebacks two hours after the situation in which she could have used them."

In this sentence, an error occurs when the possessive plural pronoun "their" is used to refer to a singular masculine antecedent, "Bob." Instead of using the plural possessive pronoun "their," one should use the singular masculine possessive pronoun "his."

Given that the descriptor "many" is used to describe "belonging," "belonging" should be plural. Therefore "belonging" should actually be "belongings."

The plural pronoun "they" refers back to the subject of the first part of the sentence, "The toucan." Since this noun is singular, the pronoun should be too. Changing "they" to "it" corrects the sentence's error. The corrected sentence reads, "The toucan is primarily recognized by its bright colors; it is painted a mixture of vibrant red, yellow, and blue."

This sentence has a singular demonstrative adjective (“this”) that does not agree with its plural noun (“claims”). These should be consistent. The corrected sentence reads, "While these claims are unverified, some people report that garlic is a powerful panacea."

This is an illogical comparison. To be grammatically correct, the sentence needs to say "John's story" or "that of John's" instead of just "John."

The use of "this" needs to be plural since it refers to multiple problems: "these problems" would be correct.