Which of the following examples demonstrates kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. An airplane flying is a clear example of kinetic energy, as it is actively moving through the air. The faster the airplane moves, the more kinetic energy it possesses due to its mass and velocity.

In contrast, the other options illustrate different concepts. A rock at rest does not have kinetic energy because it is not in motion. Ice melting involves a change of state and is related to potential energy, not kinetic. A plant growing involves physiological processes that do not equate to kinetic energy as there is no significant movement of the plant as a whole, even though it may have areas of active cell division. Thus, the most fitting example of kinetic energy from the list is indeed an airplane flying.