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?

Options:
[1]. The energy of the bicycle tire is applied in a circular motion.
[2]. The energy of the bicycle is transferred to only one wheel.
[3]. The gears and chain of the bicycle are covered with oil.
[4]. The gears and chain of the bicycle generate friction.
[4].