A body is released from rest and falls vertically in air of constant density. Which statement about the motion of the falling body is correct?
As it accelerates, its weight decreases so that its acceleration decreases until it travels with constant velocity.
It accelerates initially at 
but the drag force increases so its acceleration decreases.
Its velocity increases at a constant rate until its velocity becomes constant.
The drag force of the air increases continually and eventually the velocity decreases
