Choose the one compound within each set meets that meets the indicated criterrion :

Answer

`a-p;b-r;c-s;d-s`

Explanation

a=p,b=r,c=s,d=q
(a) Substitution takes place in only compound (4) , HBr will be elimunated hence elimnation reaction ,Not substion,Hence comound (!)
Williasom ether sythesis sythersis `implies` subsitution can not take place on benene hence compound (3).
Aq.ethanol will substiute `Br^(-) with H^(+)` ions relesaed in the solution turning the solution acidic in compound ($) Hence compound (4) .(d) In compound (3) ,after cjleavage ,postive charge will be on benzene ring which is highly unstable Hence compound (2).