#### Answer

A

#### Work Step by Step

A. From the definition of arccos,
x is the number from $[0, \pi]$ for which $\cos x=-1.$
$\pi\in [0, \pi] $and $\cos\pi=-1.$ so
$\pi$ is the solution.
B. From the definition of arccos,
x is the number from $[0, \pi]$ for which $\cos x=$+$1.$
$\pi\in [0, \pi] $and $\cos\pi=-1.$ so
$\pi$ is NOT the solution.
C. From the definition of arcsin,
x is the number from $[-\displaystyle \frac{\pi}{2}, \displaystyle \frac{\pi}{2}]$ for which $\sin x=-$1.
$\pi\not\in [-\displaystyle \frac{\pi}{2}, \displaystyle \frac{\pi}{2}]$ so
$\pi$ is NOT the solution.