The correct option is B Z > Y > X > W
Rate of halogenation depends upon the stability of alkyl radical formed.
As we know, tertiary free radical is the most stable, so option (Y) and option (Z) will react more faster than other two options as these two will form tertiary free radical as intermediate. In between option (Y) and (Z), option (Z) will react more towards chlorination because it has 9 α−Hs, so the radical will be more stable than option (Y) because it has 8 α−Hs. Option (W) will form primary radical as intermediate and option (X) will form secondary radical as intermediate. So, the correct order will be Z > Y > X > W