MCQ
be fastest when $R$ is
- ✓$-CH_3$
- B$-CH_2CH_3$
- C$\begin{array}{*{20}{c}}
{ - CH - C{H_3}} \\
{\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\
{\,\,\,C{H_3}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}
\end{array}$ - D$\begin{matrix}
\begin{matrix}
\,\,\,\,\,\,C{{H}_{3}\,\,\,\,} \\
|\,\,\,\,\,\, \\
\end{matrix}\,\,\,\,\,\,\,\,\,\, \\
-C-C{{H}_{3}} \\
|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
C{{H}_{3}}\,\,\,\,\,\, \\
\end{matrix}$
