Here, the pronoun “they” does not agree in number with its antecedent, “a new player.” The pronoun is plural and the antecedent is singular. The corrected sentence might read: "A new player might take some time to internalize all of the complicated rules of the game, but he or she will become an expert with some practice."

In this sentence, the people who have trouble sleeping are the "guests." Therefore, in order to maintain continuity within the sentence, "you" should not be used, as "you" does not refer to the "guests." The plural third-person pronoun "they" should be used instead.

The possessive pronoun "their" in this sentence is meant to refer to the noun "leader." Because"their" is plural whereas "leader" is singular, the pronoun should be singular as well—"his or her" instead of "their."

The answer choice "do so" is correct because it simply replaces a verb phrase mentioned earlier in the sentence—"inspire their constituents."

The answer choice "maintaining" is correct because it preserves the parallel structure started by "cultivating."

The answer choice "with" is correct because to say "peace with" something or someone is the proper use of the idiom. 

In this sentence, it is easy to think that "it" refers to "cleaning crew," but since "cleaning crew" appears as the object of the preposition "of the cleaning crew" in the subject "the members of the cleaning crew," the plural noun "members" is actually the referent of the singular pronoun "it." To correct the sentence's error, "it" should be changed to "they," which agrees with plural antecedents. The corrected sentence reads, "The members of the cleaning crew made the event enjoyable and safe for all, and they deserve our thanks."

The pronoun "her" does not agree in number with the plural subject, "Jessica and Theresa." It should be "their."

Since his friends are people, the relative pronoun “who” is more appropriate than “which.” The corrected sentence reads, "Little did he know that his two best friends, who had mistakenly thought it was his birthday, were waiting in the next room to surprise him."

Students are not things or concepts; they are people! When people are referenced, the word "who" or "whom" is used. Since the students are the subject, the word "which" should be replaced with "who."

In this sentence, the pronoun “their” does not correspond in number with its antecedent “an anthropologist.” “Their” is plural, but there is only one anthropologist. The corrected sentence reads, "An anthropologist always needs to ensure that his or her notes are meticulous and organized; detailed and accessible records are key to successful fieldwork."

In this sentence, the pronoun “their” does not match in number with its antecedent “a politician.” The pronoun is plural and the antecedent is singular. The corrected sentence would read: A politician has to choose his or her words carefully; political opponents and the media are always eager for a compromising quote.

This sentence uses the preposition “it” to refer to the actions of uprooting weeds and planting a garden. “It” should refer to a thing, not an action. A more appropriate choice would be “so”: "He had wanted to uproot the weeds in the backyard and plant a real garden, but he never seemed to have time to do so."