Given $f(x)=x^{3}-9 x^{2}+24 x-6$ , at Which Value(s)of X Does the Curve Have a the Curve

Multiple Choice

Given $f(x) =x^{3}-9 x^{2}+24 x-6$
, at which value(s) of x does the curve have a horizontal tangent?

A) 1
B) 2
C) 3
D) 4
E) 5