Final answer:
Option A. Jack stands are used to provide a stable support under a lifted vehicle to prevent it from falling, ensuring the safety of anyone working underneath.
Step-by-step explanation:
Jack stands should be placed under lifted vehicles to prevent the vehicles from falling. This is a critical safety practice in vehicle maintenance and repair. When a vehicle is lifted, whether by a hydraulic jack or other means, it is essential to use jack stands to provide a stable and secure support to hold up the car. Jack stands prevent a vehicle from collapsing unexpectedly, which could cause serious injury or death to someone working underneath. Additionally, they ensure the vehicle does not move or shift weight in a way that could lead to an accident.
While jack stands cannot prevent a vehicle from leaning or rolling on a slope (which would require wheel chocks), their primary role is to maintain the vehicle's elevation and protect against the serious risk of falling. Jack stands should be placed under lifted vehicles to prevent the vehicles from falling. Jack stands provide additional support and stability to ensure that the vehicle remains in a stationary position and does not collapse or fall down. It is important to use jack stands when working under a raised vehicle to prioritize safety and prevent accidents.