reduce the cost of the watch. provide an energy source for the watch. make the watch more attractive. stop the watch from speeding up.
I am hesitating between 4 options to answer the following question, which option should I choose?
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
Possibilities:
- reduce the cost of the watch.
- provide an energy source for the watch.
- make the watch more attractive.
- stop the watch from speeding up.

provide an energy source for the watch.