Final answer:
A) equal to the bucket's weight. The tension in the rope is equal to the bucket's weight.
Step-by-step explanation:
Tension in the rope when a person is lowering a bucket into a well with a massless rope at a constant speed is equal to the bucket's weight (option A). This is because the bucket is in equilibrium, which means the net force acting on it is zero. The only two forces acting on the bucket are its weight and the tension in the rope. According to Newton's second law, the net force on an object in equilibrium is zero. Therefore, the tension in the rope must be equal to the bucket's weight.