$PCI _5( g ) \rightleftharpoons PCl _3( g )+ Cl _2( g )$
(Case \(1:\) At constant \(P\) - volume will increase so reaction will shift in forward direction then answer will be \(A\)
Case \(2:\) At constant volume no change in active mass so reaction will not shift in any direction then answer will be \(D\).
$C _{2} H _{5} OH + PCl _{3} \rightarrow C _{2} H _{5} Cl + A$
$A + PCl _{3} \rightarrow B$