The main difference between free weights and a universal machine is best captured by:
B. Universal machines are safer because the weights are not above the body.
Universal machines often provide guided motion, which can reduce the risk of injury, especially for beginners, as they help to stabilize the movement and control the weights more effectively. Free weights require more stabilization and proper form, which can be beneficial for building functional strength, but they can also carry a higher risk of injury if not used correctly.