A Sealed Hot Air Balloon Is Capable of Rising to High

Multiple Choice

A sealed hot air balloon is capable of rising to high altitudes when it is initially released. As the air in the balloon cools, however, it eventually comes back down to the ground because

A) what goes up must come down.
B) objects heavier than air can only fly through the air with the help of a motor.
C) the object comes down when the air in it eventually leaks out.
D) objects can only float in a fluid if their density is less than that of the fluid.
Fill in the Blank Questions