Which of the following is correct regarding the construction of an air-cooled diesel stacker engine?

The construction of an air-cooled diesel engine relies on the design elements that facilitate cooling without the need for liquid coolant systems, such as those utilizing water jackets or oil cooling. The option indicating "Cylinder without water jacket" accurately reflects this characteristic. Air-cooled engines are designed to dissipate heat directly into the surrounding air, allowing for lightweight construction and reduced complexity compared to liquid-cooled systems.

In air-cooled systems, the absence of a water jacket means that the engine relies solely on airflow to maintain a suitable operating temperature. This can be advantageous in applications like stacker engines, where simplicity and efficiency are key considerations.

Other configurations mentioned, such as those involving water jackets or oil cooling, are typical in liquid-cooled engines, which do not apply to the design of air-cooled diesel engines. Additionally, while forced air cooling may seem applicable, it still implies a cooling method that utilizes external air flow but does not negate the fact that the cylinder in question does not incorporate a water jacket. Hence, the correct choice emphasizes the specific construction that defines air-cooled diesel engines.