The correct answer is A. Reduce slightly.
A DC shunt motor is a type of electric motor that uses a DC power source to create a magnetic field that rotates the motor’s shaft. The speed of a DC shunt motor is determined by the amount of current flowing through the motor’s field coils. When the load on the motor is increased, the current flowing through the field coils decreases, which causes the motor’s speed to decrease slightly.
Option B is incorrect because the speed of a DC shunt motor does not increase slightly when the load is increased. Option C is incorrect because the speed of a DC shunt motor does not increase proportionately when the load is increased. Option D is incorrect because the speed of a DC shunt motor does not remain unchanged when the load is increased.