Which of the following components is primarily responsible for protecting the car's passengers in a rollover accident?

The roof structure plays a critical role in protecting passengers during a rollover accident. In such incidents, the vehicle may roll over onto its side or roof, and the roof is designed to maintain integrity under these circumstances. A strong roof structure helps prevent collapse, which reduces the risk of injury to the occupants.

Modern vehicles often undergo rigorous testing to ensure that the roof can withstand specific forces, thereby meeting safety standards that aim to protect passengers during rollovers. Additionally, the presence of rollover protection systems, which are integrated into the roof structure, further enhances safety by absorbing impact forces.

While side skirts, bumpers, and fenders contribute to the overall safety and structural integrity of a vehicle in various accidents, they do not serve the primary function of protecting occupants in rollover situations. Their roles are more aligned with handling other types of collisions and providing aesthetics or aerodynamics. Thus, the roof structure is the most significant component in guarding against injuries in rollover accidents.