There are two important fuels A and B both of which are extracted from deep inside the earth. Fuel A is a thick, dark, foul-smelling liquid whereas fuel B is a black solid. Combustion of both the fuels produces products, C, D, E and F. The product C makes the rainwater only slightly acidic but it is mainly responsible for causing global warming. The product D is neither acidic nor basic. It is harmless and does not affect the environment in any way. Both E and F attack breathing system of humans and are mainly responsible for causing acid rain. In addition to combustion of fuels A and B, the product F is also formed when lightning occurs in the sky. (a) What are (i) fuel A, and (ii) fuel B? (b) Name (i) C (ii) D (iii) E, and (iv) F (c) What is the process of formation of F during lightening known as? (d) Which fuel is supposed to be exhausted sooner: A or B? (e) Which fuel is mostly used for generating electricity at thermal power plants?