"They," a plural pronoun, is used in the sentence to refer to "the mongoose," a singular subject. So, "they" should be changed to "it."

"Their" is a possessive pronoun that indicates that an object belongs to several owners. However, this sentence refers to a single actress, so the lines only belong to one person. Therefore, the best pronoun to use is "her" because it matches the singular nature of the subject: she should study her lines. The correct sentence would be "An actress who struggles with memorization should study her lines daily."

Whenever a sentence refers to a person of unknown gender and a singular possessive pronoun is required that refers to that person, one typically includes both the masculine and the feminine possessive pronouns in the phrase "his or her." In this case, "his or her" is a better choice than "their" because "student" is a singular noun, and "their," which is a plural pronoun, does not agree with it in number. Considering the other potential answer choices, "they're" is the contraction of "they are," which would not make sense in the sentence, "it's" is the contraction of "it is," which wouldn't make sense in the sentence either, and "its" is the possessive form of the pronoun "it," which is not used to refer to a person. So, none of those answer choices can be correct.

The original text contains a pronoun agreement error. The intended antecedent of the pronoun "it" is supposed to be "books," which is plural and would therefore require the plural pronoun "them" instead of the singular pronoun "it."

The only answer choices that contain "them" instead of "it" are "that cause them to decay" and "that causes them to decay." The answer choice with "causes," however, uses this singular verb with a plural subject, "materials," and is therefore incorrect.

The original text "the person who has most significantly transformed the world through their charitable actions or scientific discoveries" and the answer choice "the person who most significantly transformed the world through their charitable actions or scientific discoveries" contain pronoun agreement errors because they incorrectly use the plural pronoun "their" to refer to the singular noun "person."

The answer choices "the person that has most significantly transformed the world through his or her charitable actions or scientific discoveries" and "the person that significantly transformed the world through his or her charitable actions or scientific discoveries" are incorrect because they use "that" to refer to a person, when "who" or "whom" should be used when referring to a person. (Remember to use "that" only when referring to non-human living things or objects.)

The answer choice "the person who has most significantly transformed the world through his or her charitable actions or scientific discoveries" is correct because it is the only answer choice that correctly uses "who" and the singular pronoun "his or her" to match the singular noun "person."

The pronoun refers to employees, so the pronoun should be plural rather than the singular he or she.

The use of "your" at the end of the sentence is confusing, as the only reference in the sentence is "a person," and the second person pronoun has no place in the sentence. Changing "your" to a third person possessive pronoun will straighten out this problem. Because we do not know whether the "person" in question is male or female, we should use the phrase "his or her." The correct answer choice, therefore, is "for the rest of his or her life."

The phrase as written in the underlined portion makes an odd reference. The subject of the sentence are the "rites," and not the religion. The faith needs to be specifically referenced, as well as being fully grammatically correct; therefore, "after the faith was no longer active" is the correct answer choice.

The error in the underlined portion of the sentence is its use of the singular form "part" after the adjectives "many different." As both adjectives indicate the plurality of the noun they describe, the singular noun "part" needs to be a plural noun to correct the error. "Many different parts of the world" is the correct answer choice because it is the only one in which this error is corrected.

The key issue with the underlined phrase is the simultaneous use of "an" and the plural form "studies." Either the singular "an" or the plural "studies" needs to be changed to make the forms match. "An objective study" is the correct answer choice.