stroking the coil with a piece of silk heating the coil uniformly laying the coil near a magnet rotating the coil in a magnetic field
I gave my students this multiple choice question: Which is the best way to generate an electrical current in a coil of wire?

Only one answer is correct among these 4 choices:
- stroking the coil with a piece of silk
- heating the coil uniformly
- laying the coil near a magnet
- rotating the coil in a magnetic field

Could you tell me which one is correct?

rotating the coil in a magnetic field