The astronauts in International Space Station are in an afloat state. Why?
A. Because of their distance from Earth, the gravitational force of the earth on them is very small.
B. Because their distance from Earth, the gravitational force of the earth on them is precisely zero.
C. They are afloat because they are constantly in free fall and will eventually crash to earth.
D. They are afloat because they are constantly in free fall and because of their tangential move in an orbit.
E. They are afloat because they are bunch of show-offs and have nothing better to do up there.