Which of the following is a polar aprotic solvent?

Classify the following reactions into one of the reaction types studied in this unit:
$(a)$ $CH_3CH_2Br + HS^{-} \rightarrow CH_3CH_2SH + Br^{-}$
$(b)$ $(CH_3)_2C=CH_2 + HCl \rightarrow (CH_3)_2ClC-CH_3$
$(c)$ $CH_3CH_2Br + HO^{-} \rightarrow CH_2=CH_2 + H_2O + Br^{-}$
$(d)$ $(CH_3)_3C-CH_2OH + HBr \rightarrow (CH_3)_2CBr-CH_2CH_3 + H_2O$

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:

The rate of $\beta$-dehydrohalogenation in the following halides under treatment with a strong base follows the order:

Which compound in each of the following pairs will react faster in $S_N2$ reaction with $OH^{-}$?
$(i)$ $CH_3-Br$ or $CH_3-I$
$(ii)$ $CH_3-C(CH_3)_2-Cl$ or $CH_3-Cl$

The total number of optically active compounds formed in the following reaction is
$CH_3CH_2C(CH_3)=CHOCH(CH_3)_2$ $\xrightarrow{HBr}$