Think about a moving coil microphone. Then, with reference to it, pick out the odd one from the following given options.
A microphone is a device that converts sound waves into an electrical signal. Permanent magnet, diaphragm and voice coil are parts of moving coil microphone (refer the given diagram). It works on the basis of electromagnetic induction by converting sound vibrations into electrical signals. Here, option (B) is the odd one as it is the parts of an AC generator, not a part of a microphone.