The major product formed in the following reaction is:

Match the reactants in Column-$I$ with the major products in Column-$II$.

Column-$I$ (Reactants)	Column-$II$ (Products)
$(A)$ $HCHO + \text{Cyclohexyl-MgBr} \rightarrow X \xrightarrow{H_2O} Y$	$(i)$ $\text{Benzenesulfonic acid}$
$(B)$ $\text{2-oxocyclohexylacetate} \xrightarrow{NaBH_4}$	$(ii)$ $\text{Cyclohexylmethanol}$
$(C)$ $HCHO + CH_3-CH_2-CH(CH_3)-CH_2-MgBr \rightarrow X \xrightarrow{H_2O} Y$	$(iii)$ $\text{2-(2-hydroxycyclohexyl)acetate}$
$(D)$ $\text{Benzene} + \text{Oleum}$	$(iv)$ $Y = \text{3-methylpentan-1-ol}$

$C_2H_5CHO$ and $(CH_3)_2CO$ can be distinguished by testing with

$A$ reaction of benzonitrile with one equivalent of $CH_{3}MgBr$ followed by hydrolysis produces a yellow liquid $P$. The compound $P$ will give a positive result for which of the following tests?

The end product $(C)$ in the following reaction is:

What is Tollen's reagent?