What should you never do while a jack is lifting a vehicle?

When a jack is lifting a vehicle, it is crucial to prioritize safety, and one of the most essential safety practices is to avoid placing any body part under the vehicle. This is because a jack can fail or become unstable, leading to a sudden drop of the vehicle, which can cause severe injury or even fatality if a person is underneath it. Understanding this safety measure is key to preventing accidents in the workplace.

While the other responses relate to caution and safety, they do not carry the same immediate life-threatening risk as positioning body parts under a raised vehicle. Stepping away from the vehicle or using a cellphone may still allow for safer monitoring of the situation, while adjusting the jack's position can be performed safely if done correctly and with appropriate precautions.