Which component of the engine is responsible for opening and closing to allow airflow?

The component of the engine responsible for opening and closing to allow airflow is the valves. Valves play a critical role in the intake and exhaust processes of an engine. They open to allow air (and fuel) into the combustion chamber during the intake stroke and then close to contain the air-fuel mixture for combustion. After combustion, the exhaust valves open to let the exhaust gases exit the engine. This opening and closing mechanism is essential for maintaining the proper cycle of air and gas flow that powers the engine effectively.

In terms of the other options, pistons move up and down within the cylinders but do not control airflow directly. The camshaft, while it does influence the operation of the valves by rotating to open and close them at the right intervals, is not directly responsible for airflow itself. The crankshaft converts the linear motion of the pistons into rotational motion but does not have any direct role in the opening or closing needed for airflow. Thus, the valves are the key components that actively manage this airflow in the engine's operation.