Q7

Which statement is always true for real numbers $a$ and $b$ where $-1\leq a<b\leq1$?
A. $\sec a<\sec b$
B. $\sin^{-1}a<\sin^{-1}b$
C. $\arccos a<\arccos b$
D. $\cos^{-1}a+\sin^{-1}a<\cos^{-1}b+\sin^{-1}b$