c) Jack will not understand the club’s decision unless he talks to Christopher.
Explanation:
A vague pronoun is a pronoun that does not clearly indicate which antecedent (or noun) it is referring to. All options, except option C, have a vague pronoun because in these sentences it is not clear whether “he” (the pronoun) is referring to the antecedent “Jack” or “Christopher.”
Option C, on the other hand, is the one that corrects the vague pronoun because it clearly states that the pronoun “he” refers to “Jack” only.
