To assess the motor functions in the lower extremities of a responsive patient, you would:

Asking the patient to wiggle his toes is a focused way to assess motor functions in the lower extremities. This action specifically evaluates the ability of the muscles and nerves that control toe movement, which can indicate the functioning of the lumbar and sacral regions of the spinal cord. Additionally, wiggling toes requires coordination and muscle strength, providing insight into the overall motor capability of the lower extremities.

Other methods, such as bending the knees or moving the leg, may not directly assess individual muscle groups or can involve assistance from the examiner, which may not give an accurate indication of motor function. Touching the skin of the patient's foot primarily evaluates sensory response rather than motor function, which is why it does not directly address the question regarding motor assessment.