What are the two cooling systems used in diesel engines?

The two primary cooling systems used in diesel engines are categorized as freshwater and seawater. Among these, freshwater cooling systems use a closed loop to circulate coolant within the engine, which helps maintain optimal operating temperatures by transferring heat away from the engine block. Seawater cooling systems, on the other hand, typically involve drawing in seawater for direct cooling, especially in marine environments where the engine is used.

The first option incorrectly suggests internal pressurized and raw water, which does not accurately represent the standard terminology commonly used in describing cooling systems for diesel engines. It's essential to understand the context of cooling in diesel engines, especially for those used in marine applications, where efficient heat dissipation is critical for reliable performance. The other choices also do not align with the standard classifications typically used in engineering and maintenance of diesel engines.