Please choose the correct answer to the 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

Answer1: reduce the cost of the watch. Answer2: provide an energy source for the watch. Answer3: make the watch more attractive. Answer4: stop the watch from speeding up.

Answer format: answer1/answer2/answer3/answer4
Answer: answer2