**Core Concept**
The kinetic energy of the body is related to the movement and momentum of the body's mass during walking. The kinetic energy is determined by the velocity and mass of the body. In the walking cycle, the body's kinetic energy varies at different phases due to changes in velocity and momentum.

**Why the Correct Answer is Right**
The kinetic energy is least during the single support phase of the walking cycle. This phase occurs when one foot is in contact with the ground and the body is balanced on that foot. During this phase, the body's velocity is minimal, and the momentum is zero. As a result, the kinetic energy is at its lowest point in the walking cycle.

**Why Each Wrong Option is Incorrect**
* **Option A:** The initial contact phase is not the phase with the least kinetic energy. During this phase, the body's velocity is high, and the momentum is significant.
* **Option B:** The mid-stance phase is not the phase with the least kinetic energy. Although the body's velocity is low during this phase, the momentum is still present due to the body's mass and the force of gravity.
* **Option C:** The terminal swing phase is not the phase with the least kinetic energy. During this phase, the body's velocity is high, and the momentum is significant as the body prepares to make contact with the ground.

**Clinical Pearl / High-Yield Fact**
Remember the phases of the walking cycle: initial contact, loading response, mid-stance, terminal stance, pre-swing, and terminal swing. Each phase has distinct characteristics that affect the body's kinetic energy and momentum.

**Correct Answer:** B.