Work is done when force is applied a for a long enough period of time.
b in the opposite direction that the object moves.
C in the same direction that the object moves.
d two of the above

If football was tossed in air without gravity or friction the ball would go into space

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.

Independent variable is something that is changed in a experiment. 

For me a person with a phd and who knows what there talking about.i know the chances of a radiation leak is low but if it does the area within a 96.3 mile radius would be unusable because of contamination