What area is referred to as the sole of the foot?

The area referred to as the sole of the foot is known as the plantar surface. The term "plantar" specifically denotes the undersurface of the foot where it comes into contact with the ground. This region is crucial for walking and provides support, balance, and traction. It is an anatomical term frequently used in various medical and biological contexts.

The popliteal region pertains to the area behind the knee, which is not related to the sole of the foot. The sural area refers to the back of the leg, commonly known as the calf, and is also separate from the foot's anatomy. The tarsal area includes the bones and structures located around the ankle and in the foot's midsection but does not specifically denote the bottom surface. Thus, the term "plantar" is distinctly associated with the sole of the foot, making it the correct answer.