Insertion of resistance in the rotcir of an induction motor to develop a given torque

The correct answer is: A. decreases the rotor current.

When resistance is inserted in the rotor of an induction motor, the rotor current decreases. This is because the resistance in the rotor circuit causes a voltage drop, which reduces the current flowing through the rotor. The reduced current causes a decrease in the torque developed by the motor.

Option B is incorrect because the rotor current decreases, not increases.

Option C is incorrect because the rotor current does not become zero.

Option D is incorrect because the rotor current decreases, not remains the same.