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

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

This is Reimer-tiemann reaction.In this reaction chloroform and sodium hydroxide react to produce an $e^{\ominus}$-deficient electrophile dichlorocarbene $(:CCl_2)$
aq.$NaOH +CHCl_3\rightarrow NaCl+H_2O+:CCl_2$
Hence (a) is the correct answer.