The correct answer is: A. Separately excited generator.
A separately excited generator is a type of DC generator that uses a separate DC power supply to excite the field winding. This type of generator is often used in applications where a high level of control over the output voltage is required.
A shunt generator is a type of DC generator that uses the same DC power supply to excite the field winding and to provide the output voltage. This type of generator is often used in applications where a simple, reliable generator is required.
A series generator is a type of DC generator that uses the same DC power supply to excite the field winding and to provide the output current. This type of generator is often used in applications where a high level of starting torque is required.
A compound generator is a type of DC generator that has both a shunt field winding and a series field winding. The shunt field winding is used to provide a constant output voltage, while the series field winding is used to provide a constant output current. This type of generator is often used in applications where a high level of both starting torque and output voltage is required.
In summary, a separately excited generator is a type of DC generator that uses a separate DC power supply to excite the field winding. This type of generator is often used in applications where a high level of control over the output voltage is required.