f(x) is invertible polynomial function of degree ‘n’ {n≥3} then f"(x) = 0 has exactly ‘n – 2’ distinct real roots if

Question

$f(x)$ is invertible polynomial function of degree $n\geq 3$ then $f''(x) = 0$ has exactly $n - 2$ distinct real roots if

A)$f′(x)=0$ has $(n−1)/2$ distinct real roots

B)$f′(x)=0$ has $n−1$ distinct real roots

C)all the roots of $f′(x)=0$ are distinct

D)none of these