Fact 1: Coal is used to produce electricity by burning in coal-fire power stations. Fact 2: Electricity is really the movement of electrons. Given the two facts above, coal is used to produce the movement of electrons by what in coal-fire power stations?

Available choices:
(a). cooling
(b). energy
(c). rotating
(d). burning
(e). heat
(f). engines
(g). mining
(h). sun's heat
The answer is:
(d).