Answer:
D,
degrees
Step-by-step explanation:
Complementary angles are angles that add up to 90 degrees. Since angle A and angle B are complementary, they add up to 90. Since the value of angle A is y degrees, we can substitute y into the equation to get

To get the measure of angle B, we must isolate B.
To isolate B, we have to remove every term from its side.
The only term on the side that B is on other than B is y. To remove y from the left side, we must subtract y from both sides. Doing this will result in the equation:

The only answer option that meets this criteria is D.