Options are:
(a). silence
(b). Something to move
(c). reproduction
(d). birth
(e). energy of moving objects
(f). heat energy
(g). Chemical energy
(h). harmful substances
Given those answer options, answer the question: Fact 1: Producing thrust causes something to move. Fact 2: Then the engine spins up and starts producing thrust. Given the two facts above, what do engines cause?
A:
(b).