The correct answer is: C. Number of poles is 4.
A DC generator is a device that converts mechanical energy into electrical energy. It does this by using a rotating magnetic field to induce an electric current in a stationary conductor. The number of mechanical degrees and electrical degrees will be the same when the number of poles is 4. This is because the magnetic field will rotate 360 degrees in 4 electrical cycles.
When the number of poles is 2, the magnetic field will rotate 180 degrees in 2 electrical cycles. This means that the number of mechanical degrees will be twice the number of electrical degrees.
When the number of poles is 3, the magnetic field will rotate 270 degrees in 3 electrical cycles. This means that the number of mechanical degrees will be 3 times the number of electrical degrees.
When the number of poles is 4, the magnetic field will rotate 360 degrees in 4 electrical cycles. This means that the number of mechanical degrees will be the same as the number of electrical degrees.