A parachutist is in free fall before opening her chute. The net force on her has magnitude F and is directed down; this net force is somewhat less than her weight W because of air friction. Then she opens her chute. At this instant after her chute fully inflates the net force o her is

(A) greater then F and still directed down.

(B) less than F and still directed down.

(C) zero.

(D) directed upward but could be more or less than F.

The correct option is (B) less than F and still directed down.
If W is the weight of the system, f is the drag force of the system and since the net force (F) is directed down, then the net force acting on the system (F) will be,
F = W-f …… (1)
When she opens her chute, the drag force (f) will be increased. So increasing the drag force the right hand side of the equation (1) will be decreased results the net force on the on her (left hand side of equation (1) ) is decreased. Therefore when she opens her chute, the net force on her is less than F and still directed down.
From above observation we conclude that, at the instant after her chute fully inflates the net force on her is less than F and still directed down. Thus option (B) is correct.