Final answer:
The term for when neither foot is in contact with the ground is 'nonsupport.' This phase commonly occurs during running and is distinct from single support, double support, and swing phases of gait. the correct option is (d).
Step-by-step explanation:
The time when neither foot is in contact with the ground while walking or running is known as the nonsupport phase. The options provided suggest various phases of gait or body postures, but for the specific condition where neither foot touches the ground, the correct term is nonsupport. This occurs during dynamic activities such as running when both feet are in the air, typically between the end of the swing phase of one foot and the beginning of the stance phase of the other.
In contrast, single support refers to when only one foot is on the ground, double support refers to when both feet are on the ground, and swing phase is when one foot is off the ground and swinging forward. Therefore, the correct answer to the question is d. nonsupport.