Which component is described as the shaft on which the wheels revolve?

The axle is the component that serves as the shaft on which the wheels revolve. It is a crucial part of the vehicle's drivetrain and suspension system, connecting the wheels and allowing them to rotate and support the weight of the vehicle. The axle also provides stability and helps in transferring the power generated by the engine to the wheels, enabling movement. This component is essential in various types of vehicles, contributing to overall driveability and performance.

In contrast, the hub is the central part of the wheel that connects it to the axle, allowing it to rotate smoothly. The spindle acts as a pivot point for the wheel assembly and is involved in the steering mechanism but is not where the wheels directly revolve. The chassis is the frame of the vehicle, which supports all other components, but it does not function as the rotating shaft for the wheels themselves. This distinction highlights why the axle is correctly identified as the component upon which the wheels revolve.