Which equation could be used to solve problems involving the relationships between the angles?

A. 90 + (8a + 9) = (11 + 2a)
B. 90 − (8a + 9) = (11 + 2a)
C. (11 + 2a) − 90 = (8a + 9)
D. (8a + 9) − (11 + 2a) = 90