The correct answer is B) higher compression pressures. Diesel engines have higher compression ratios than gasoline engines, which results in higher compression pressures. These higher compression pressures require a more powerful starter motor to overcome the greater resistance and crank the engine. Diesel starter motors need to be heavier duty and operate at higher voltages compared to gasoline engine starters to provide the necessary cranking power. The other options are incorrect because: A) flywheel effect is not the primary reason, C) lower starting temperatures do not require higher-powered starters, and D) higher speed is not the key factor, as the starter just needs to provide enough torque to crank the engine.