Prolonged exposure of chloroform in humans may cause damage to the liver. It is due to the formation of the following compound.

For each of the following pairs of $E_2$ reactions,select the one that occurs with the greater rate constant:
$(1)$ $CH_3-CH_2-CH_2-Cl + CH_3-C(CH_3)_2-O^-$
$(2)$ $CH_3-CH_2-CH_2-I + CH_3-C(CH_3)_2-O^-$
$(3)$ $CH_3-CH(Br)-CH_3 + CH_3-O^-$
$(4)$ $CH_3-CH(Br)-CH_3 + CH_3-S^-$
$(5)$ $Ph-CH_2-CH(Br)-CH_2-CH_3 + OH^-$
$(6)$ $Ph-CH_2-CH_2-CH(Br)-CH_3 + OH^-$

Vinylcyclopentane $\xrightarrow{HCl}$ Major product is

The isomeric deuterated bromide with molecular formula $C_4H_8DBr$ having two chiral carbon atoms is

When ethanol is reacted with $PCl_5$,it gives $A$,$POCl_3$,and $HCl$. Compound $A$ reacts with silver nitrite to give the major product $B$ and $AgCl$. What are $A$ and $B$ respectively?

The major product obtained in the given reaction is: