Final answer:
A patient should stand on the unaffected leg while using crutches. Other positions mentioned are body positions and unrelated to crutch use.
Step-by-step explanation:
When using crutches, a patient should stand on the unaffected leg. This means that when a person needs to use crutches due to an injury or surgery, they should lean on the leg that is not affected while the injured leg (affected leg) is kept off the ground or touched lightly if allowed by the physician. It's important for the safety and recovery of the patient to use the proper technique with crutches. The options provided, such as the person being prone or supine, are body positions and do not relate to the use of crutches.