An organic compound $A$ $(C_4H_9Cl)$ on reaction with $Na$ in diethyl ether gives a hydrocarbon,which on monochlorination gives only one chloro derivative. $A$ is:

The following reaction belongs to $(CH_3)_3CBr \xrightarrow{H_2O} (CH_3)_3COH$.

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $R-I$ undergoes $S_N2$ reaction faster than $R-Cl$.
Reason $(R):$ Iodine is a better leaving group because of its large size.
In the light of the above statements,choose the correct answer from the options given below:

Chloroform is slowly oxidized by air in the presence of light to form:

$C_2H_5Cl + KCN$ $\xrightarrow{} X$ $\xrightarrow{\text{Hydrolysis}} Y.$
$X$ and $Y$ are:

The reaction of $1$-chlorobutane with alcoholic potash gives $......$.