They were more intelegent
The first alternative is correct (A).
Stretching is a way to stimulate the muscles and ligaments of the human body to improve posture, breathing and pre-disposition of people. Several activities are part of stretching, such as correct breath control, the time each session should last, and the natural discomfort. However, bounceing the body is not part of stretching practices, it is part of some aerobic activities.
