The correct answer is: B. Line losses.
Line losses are the losses of electrical energy that occur in the transmission and distribution of electricity. These losses are caused by the resistance of the conductors and the inductance of the lines. The higher the voltage, the lower the line losses.
DC generators are installed near the load centers to reduce line losses. This is because DC generators have a higher efficiency than AC generators. The efficiency of a generator is the ratio of the output power to the input power. The efficiency of a DC generator is higher than the efficiency of an AC generator because there are no losses due to the commutator and brushes.
The other options are incorrect because:
- Iron losses are the losses of electrical energy that occur in the iron core of the generator. These losses are caused by the eddy currents and hysteresis losses.
- Sparking is the discharge of electricity between two conductors. This can occur when the voltage between the conductors is high enough.
- Corona losses are the losses of electrical energy that occur in the corona discharge. This is a discharge of electricity that occurs in the air around a conductor when the voltage is high enough.