C

- Hướng dẫn giải

Ta có \(f'\left( x \right) =  - 4{x^3} + 24x\)

\(f'\left( x \right) = 0 \Leftrightarrow  - 4{x^3} + 24x = 0 \Leftrightarrow \left[ \begin{array}{l}
x = 0 \in \left[ { - 1;2} \right]\\
x = \sqrt 6  \notin \left[ { - 1;2} \right]\\
x =  - \sqrt 6  \notin \left[ { - 1;2} \right]
\end{array} \right.\)

\(f\left( { - 1} \right) = 12,\,f\left( 2 \right) = 33,\,f\left( 0 \right) = 1.\)

Vậy \(\mathop {\max }\limits_{\left[ { - 1;2} \right]} f\left( x \right) = f\left( 2 \right) = 33\)