Answer:
Option b. is correct.
Explanation:
In the given question a parachutist is falling toward the ground .
Also, the downward force of gravity is exactly equal to the upward force of air resistance.
So, net force applied to the parachutist is equal to zero ( because both force acts in opposite direction ).
Now by first law of motion :
An object will be in rest or in constant speed unless and until no external force is applied on it .
So, in the question the velocity of the parachutist is not changing with time.
Therefore, option b. is correct.
Hence, this is the required solution.