Which one of the following engines will have heavier flywheel than the remaining ones?

A. 30 kW four-stroke petrol engine running at 1500 r.p.m.

B. 30 kW two-stroke petrol engine running at 1500 r.p.m.

C. 30 kW two-stroke diesel engine running at 750 r.p.m.

D. 30 kW four-stroke diesel engine running at 750 r.p.m.