What structure is designed with crumple zones to absorb impact and is made of sheet metal panels welded together?

The correct answer is unibody. Unibody construction is characterized by a design approach where the body of the vehicle is constructed as a single cohesive unit. This design allows the vehicle to effectively incorporate crumple zones, which are areas specifically engineered to deform and absorb energy during a collision. The integration of these crumple zones helps to protect occupants by reducing the forces transmitted to them during an impact.

The unibody structure, made of sheet metal panels that are welded together, contributes to the overall rigidity and strength of the vehicle while also enhancing its safety features. Sheet metal provides the necessary strength to maintain the vehicle's shape under various conditions, while the welding process ensures that the components are tightly joined, improving structural integrity.

The other choices represent different structural designs used in vehicle construction. A subframe supports components like the engine and suspension but does not inherently have the same level of integration and energy absorption characteristics as a unibody design. A body-on-frame construction separates the body from the frame, leading to less effective crumple zones. The chassis refers to the vehicle’s framework that houses the drive components but does not encompass the entire safety design and impact absorption features found in a unibody.