Which one of the following reagents is used in the below reaction?

Question

 

$\begin{array}{1 1}(a)\;aq.NaOH+CHCl_3&(b)\;aq.NaOH+CH_2Cl_2\\(c)\;aq.NaOH+CCl_4&(d)\;aq.NaOH+CCl_4\end{array}$