The correct option is B BeCl2
When a mixture of beryllium oxide (X), carbon and chlorine is heated, a mixture of beryllium dichloride (Y) and carbon monoxide is obtained.
BeO+C+Cl2→BeCl2+CO
The hydrolysis of beryllium dichloride gives beryllium hydroxide (Z) and HCl.
BeCl2+2H2O→Be(OH)2+2HCl
Beryllium dichloride is electron deficient and is found in polymeric chains.