Magnetic field in a D.C. generator is produced by

Answer: Option C

In a D.C. generator, the magnetic field is essential for the generation of electricity through electromagnetic induction.

Most commonly, this magnetic field is produced by electromagnets which are created by field windings supplied with direct current.

However, in small D.C. generators or specific applications, permanent magnets can also be used to produce the magnetic field.

Therefore, depending on the type and size of the generator, both electromagnets and permanent magnets may be used.

Hence, the correct answer is Option C: Both (A) and (B)