Answer:
D) when one angle is acute and the other is obtuse.
Explanation:
A linear pair of angles are formed when two adjacent angles are supplementary, meaning their measures add up to 180 degrees. In this case, if one angle is acute (less than 90 degrees) and the other angle is obtuse (greater than 90 degrees), their measures can add up to 180 degrees and form a linear pair.
For example, let's consider angle A as 60 degrees (acute) and angle B as 120 degrees (obtuse). The sum of these angles is 60 + 120 = 180 degrees, fulfilling the requirement for a linear pair.