Fact 1: When an animal moves , chemical energy is converted to mechanical energy.  Fact 2: Cows are social animals.  Given the two facts above, what converts chemical energy to mechanical energy when it moves?
Available choices: (i) Birds. (ii) bears. (iii) cows. (iv) Whales. (v) toads. (vi) hawks. (vii) cars. (viii) fish.
Answer:
(iii)