Rolle’s theorem can not applicable for

• A

  $f\left(x\right)=\sqrt{1-x^2}$  in $\left[-1,1\right]$

• B

  $f\left(x\right)=\left|x\right|$  in $\left[-1,1\right]$

• C

  $f\left(x\right)=x^2-1$  in $\left[-1,1\right]$

• D

  $f\left(x\right)=x^3+x^2-x-1$  in $\left[-1,1\right]$