c
\(\begin{matrix}
\,\,\,\,O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,O\,\,\,\,\,\,\,\\
\,\,\,\,||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,||\,\,\,\,\,\,\, \\
C{{H}_{3}}-C-C{{H}_{2}}-C-O-Et \\
\end{matrix}\) \(\xrightarrow{C{{H}_{3}}MgBr}\) \(\begin{matrix}
O\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
||\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
C{{H}_{3}}-C-\underset{\overset{\oplus }{\mathop{M}}\,gBr}{\mathop{\overset{\Theta }{\mathop{C}}\,H}}\,-C{{O}_{2}}Et \\
\end{matrix}\)
(because of active methylene group acid-base take place).