#### Answer

C

#### Work Step by Step

Use the definitions of circular functions.
A. x is a number from $(-\displaystyle \frac{\pi}{2}, \displaystyle \frac{\pi}{2})$, for which $\tan x=1.$
Since $\tan 0=0\neq 1,$
zero is not the solution ($x\neq 0)$
B. x is a number from $[0, \pi]$ for which $\cos x=0$
Since $\cos 0=1\neq$0,
zero is not the solution ($x\neq 0)$
$C. $x is a number from $[-\displaystyle \frac{\pi}{2}, \displaystyle \frac{\pi}{2}]$ for which $\sin x=0$
Since $\sin 0=0$,
0 is the solution