Find the Point(s) of Inflection of the Graph Of $f(x)=\cos ^{-1} 7 x$

Multiple Choice

Find the point(s) of inflection of the graph of $f(x) =\cos ^{-1} 7 x$

A) $(1,0)$ , $\left(0, \frac{\pi}{2}\right)$ , and $\left(0, \frac{\pi}{7}\right)$
B) $(1,0)$
C) $\left(0, \frac{\pi}{7}\right)$
D) $\left(0, \frac{\pi}{2}\right)$