Explanation

The problem contains the phrase “must be,” so try to find numbers to plug in that disprove four of the five answer choices.

If a = 4 and ab = –12, then b = –3; eliminate choices (B), (D), and (E). Now determine whether b must be an integer. If a = 4 and ab = –2, then b
=\(\frac{-1}{2}\) ; eliminate choice (C), and you’re left with choice (A), the correct answer.