单项选择题 A crankshaft whose center of gravity coincides with its center line is said to be（） Ⅰ.statically balanced Ⅱ.dynamically balanced

单项选择题 In a trunk type diesel engine piston, the thickness of the head or crown is determined by the（） Ⅰ.statically balanced Ⅱ.heat dissipation requirement

单项选择题 A condition contributing to diesel engine piston rings sticking in the ring grooves, is insufficient ring clearance at the ring（） Ⅰ.gap Ⅱ.side