The energy of the bicycle tire is applied in a circular motion. The energy of the bicycle is transferred to only one wheel. The gears and chain of the bicycle are covered with oil. The gears and chain of the bicycle generate friction.
I gave my students this multiple choice question: Emily is riding her bicycle. Which best explains why only some of the energy used to pedal her bicycle is transferred into forward motion of the bicycle?

Only one answer is correct among these 4 choices:
- The energy of the bicycle tire is applied in a circular motion.
- The energy of the bicycle is transferred to only one wheel.
- The gears and chain of the bicycle are covered with oil.
- The gears and chain of the bicycle generate friction.

Could you tell me which one is correct?

The gears and chain of the bicycle generate friction.