The substance W is a fossil fuel. It occurs deep below the ground in certain areas of the earth. Another fossil fuel X is found trapped above the deposits of W. When W is subjected to a process called Y, then a number of different products are collected at different temperature ranges which are put to different uses. A special grade of product Z obtained in this way is used as aviation fuel in jet aeroplanes.

(a) What are (i) W and (ii) X ?

(b) What is the physical state of (i) W and (ii) X ?

(c) Name the process Y.

(d) Name the product Z.