Final answer:
The correct answer is option A. When the exterior sides of two adjacent angles are perpendicular, the angles are complementary because they each measure 90 degrees and together sum up to 180 degrees.
Step-by-step explanation:
If the exterior sides of two adjacent angles are perpendicular, this means the two angles together make a 90-degree angle. Considering that adjacent angles together make up a straight line, which is 180 degrees, if they are also complementary (adding up to 90 degrees due to their exterior sides being perpendicular), it can be concluded that each one of the angles must be 90 degrees in itself.
In the context of geometric figures and angles, when two angles have perpendicular sides, they are essentially forming a right angle with each other. In a sense, if you can imagine a + sign where the two lines intersect at the center, this intersection represents a right angle or a 90-degree turn.
Therefore, based on the understanding of geometric concepts and the relationship between angles: They are complementary (Option A), because two adjacent angles that are both right angles would add up to 180 degrees, each being 90 degrees.