Supplementary? Vertical? Complementary? Acute?

Answer:
A. supplementary
Step-by-step explanation:
Note the angle measurements of BOC. m∠BOC = 90°
Now note that line FC is a straight line, which makes it's measurement = 180°
Subtract 90 from 180: 180 - 90 = 90°
Both are 90°, which, when combined makes a supplementary angle.