单项选择题
Diesel engine electric starting motors generally require heavier duty motors and motors and operate at higher voltages than comparable starting motors for gasoline engines due to（）
A.higher speed required B.flywheel-effect C.lower starting temperatures D.higher compression pressures
单项选择题 The size of the exhaust valve opening is （）
单项选择题 If the piston groove drain holes for the oil control rings become clogged, which of the following is likely to occur?（）
单项选择题 Many cast iron pistons are designed with heat dams, which serve to （）
