What is attached to the end of the crankshaft?

The correct answer is the flywheel. In an internal combustion engine, the flywheel is mounted on the crankshaft and plays a crucial role in the engine's operation. It helps to smooth out the power delivery of the engine by storing rotational energy. When the engine produces power during the combustion process, the flywheel absorbs some of that energy and helps maintain inertia, allowing for smoother operation and continuous power delivery even when pistons are not firing.

In contrast, elements like the drive belt connect various engine components but do not attach directly to the crankshaft. The piston is an integral component of the engine that moves up and down within the cylinder, translating the combustion energy into mechanical work, but it does not attach to the crankshaft itself. A rotary pump is typically associated with circulating fluids, such as oil or fuel, and does not connect directly to the crankshaft either. Thus, the flywheel is the correct choice as it is directly attached to and supported by the crankshaft, providing stability and efficiency in the engine's operations.