Final answer:
The legs should be used to do most of the lifting when carrying heavy objects to avoid injury, as the back is not as strong and the lifting forces can be overly strenuous for the spine. correct answer is option A.
Step-by-step explanation:
To lift heavy objects safely, the legs should do most of the lifting work. When lifting with the back rounded or bent, it results in large forces exerted by the back muscles and experienced in the vertebrae. By keeping the back erect and using the strength of the leg muscles to lift, these forces on the back are significantly reduced, making it a safer practice and preventing potential injuries.
When balancing a load on the head, it's crucial for the center of mass of the load to be directly above the person's neck vertebrae to maintain balance and reduce the strain, as the muscles of the neck and back are complex and not designed to handle such exertion asymmetrically.