Find the Critical Points Of $f ( x ) = \sin x$

Multiple Choice

Find the critical points of $f ( x ) = \sin x$

A) $( 2 k + 1 ) \pi$
B) $k \pi$
C) $k \frac { \pi } { 2 }$
D) $( 2 k + 1 ) \frac { \pi } { 2 }$