Which of the following is true for two complementary angles ∠RST and ∠TSU?
Question 4 options:

A)

m∠RST + m∠TSU = 90°

B)

m∠RST + m∠TSU = 180°

C)

m∠RST = m∠TSU

D)

m∠RST = ½ × m∠TSU