Answer:
c. Both rocks will fall at the same rate.
Step-by-step explanation:
An object that moves because of the action of gravity alone is said to be free falling.
All objects free fall at the same rate regardless of their mass.
So, even though Rock S has 20 times the mass of rock T, it would not affect their rate as according to Galileo, two bodies of different masses, dropped from the same height, will touch the floor at the same time in the absence of air resistance.
Therefore, on earth, two objects of different masses fall at the same rate.