Final answer:
Plantarflexion in the gait cycle happens during the Terminal Stance phase, facilitating forward movement and walking posture.
Step-by-step explanation:
Plantarflexion occurs during the gait cycle, specifically in the terminal stance phase. This motion is characterized by lifting the heel of the foot from the ground or pointing the toes downward. It plays a critical role in propelling the body forward, as it involves lowering the sole of the foot to the ground, which is necessary when foot-tapping or jumping, and for maintaining posture while walking. In the context of the gait cycle, the correct answer to when plantarflexion occurs is option C) Terminal Stance.