A parachute attains a terminal velocity when

When an object is dropped from a height, it experiences two forces: the force of gravity, which pulls the object down, and the air resistance, which pushes the object up. As the object falls faster, the air resistance also increases until it reaches a point where the two forces are equal and opposite. At this point, the net force on the object becomes zero and it stops accelerating. This is called the terminal velocity. A parachute works by increasing the air resistance on the person wearing it. When the parachute is deployed, it catches the air and creates a large surface area. This causes the air resistance to increase, slowing down the person's descent. Eventually, the air resistance becomes large enough to balance the force of gravity on the person, and they reach their terminal velocity. Therefore, the correct answer to the question is that a parachute attains a terminal velocity when the viscous force of the air and the upthrust completely counteract its weight. Answer "the viscous force of the air and the upthrust completely counteract its weight," is the correct answer.