Pick your answer from: (a). layers of fat (b). Earth's mass (c). Time and energy (d). flow of electrons (e). kinetic energy (f). friction (g). an object (h). heat energy
Given those answer options, answer the question: You are presented with the quiz "What causes the pull of gravity?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "the mass of a planet causes the pull of gravity on that planet" and "earth is a living planet". So, what's the best answer to the question?
A:
(b).