Answer:
A. Bob twists his back to pick up the materials to feed his press machine.
Step-by-step explanation:
Ergonomic is the proper use of the mechanics of the body, in this case bob shouldn´t be twisting his back to pick up the materials he should be turning around with his whole body, this can put undesired pressure on his lower back and waist and can eventually lead to damage in the tissue, nerves and muscles.