Question: A student examines a new watch design. The watch has a small solar cell on its face. The main function of the solar cell is to

What is the correct answer to the question from the following choices?
Possible answers:
[A]. reduce the cost of the watch..
[B]. provide an energy source for the watch..
[C]. make the watch more attractive..
[D]. stop the watch from speeding up..
[B].