Given data : It is given to identify  Diethyl ether on heating with excess HI gives, from the given options.

Explanation :
As we know Ethyl iodide is $C_2{H}_{5}I$.
So diethyl ether on heating with concentrated HR reduces to ethyl iodide. 

The chemical reaction is as follows.
${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{OCH}}_2{\mathrm{CH}}_3+2\mathrm{HI}\to 2{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{I}+{\mathrm{H}}_2\mathrm{O}$

Hence, the correct option (B). $C_2{H}_{5}I$.