Which of the following has temporary magnet?

The correct answer is A: Generator 

In electricity generation, a generator is a device that converts motive power (mechanical energy) into electrical power for use in an external circuit.A generator is a machine used to convert mechanical energy into electricity. Powered by a fuel source such as oil, gasoline, wind or moving water, generators create electrical current through electromagnetic induction.Here we are using temporary magnets instead of paramagnets to avoid the loss of magnetization. When the heat dissipation more than the permanent magnets will lose the magnetization, to avoid that we are using temporary magnets in the stator.

Temporary magnets are made from soft metals, and only retain their magnetism while near a permanent magnetic field or electronic current. They become magnetized in the presence of a magnetic field. ... Paperclips, iron nails and other similar items are examples of temporary magnets.

The difference between a permanent magnet and a temporary magnet is in their atomic structures. Permanent magnets have their atoms aligned all the time. Temporary magnets have their atoms aligned only while under the influence of a strong external magnetic field.