The Constitutional Convention was called in no small part for addressi

Kaplan's Official Explanation -

In "their debate," the original sentence incorrectly uses the plural pronoun "their" to refer to the body of "the Constitutional Convention." Another problem is that "called … for addressing" uses an idiomatically incorrect preposition. A meeting is called to address an issue. Finally, the word "if" is used when a decision is between two choices (to count or not to count slaves); the correct word in this situation is "whether."

After eliminating (A), look at the remaining choices. Each starts with a different proposition. Only correct answer (C) begins with the idiomatically correct "to address," and this wording also preserves the intended meaning of the sentence.

If this detail escaped your notice, there are other differences among the choices. (B), (D), and (E) all use plural pronouns—"their" or "they"—to refer to the Convention. (C) avoids using a pronoun, substituting "the debate." In addition, (D) and (E) keep "if" instead of using "whether," so they can be eliminated for this reason as well.

TAKEAWAY: Even if you're not sure about whether an answer choice is idiomatically correct, other errors can guide you to the right answer. In this case, it was important to make sure pronouns agreed in number with their antecedent.