A12-tooth gear is turned two times. how many times will the 24-tooth gear that it is connected to turn

If the gears are perfectly coupled and they don't slip or grind,
then the number of teeth that pass on both gears in some amount
of time are equal.

-- If the 12-tooth gear makes 2 revolutions, then 24 teeth
pass the point where the gears meet.

-- 24 teeth is all the way around the second gear, so
that one revolves one time.

 

The correct answer is  "c".  it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings.