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

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

An acceptable means of tightening connecting rod and main bearing cap bolts is to measure the （）
Ⅰ.torque applied to each nut and bolt assembly
Ⅱstretch of each nut before and after tightening