Final answer:
When two rocks with different masses are dropped from the same height, they will have the same velocity just before hitting the ground.
Step-by-step explanation:
When two rocks with masses of 5kg and 10kg are dropped from a height of 20m above the ground, the statement that is true about the rocks just before they reach the ground is that they will have the same velocity. The velocity of an object in free fall is determined solely by the height from which it is dropped, not by its mass. So, both rocks will have the same velocity of 20 m/s just before they reach the ground.