单项选择题 The lower end of each piston rod is reduced in diameter to fit a bore in the （）, this being secured to the piston rod by a nut.

单项选择题 The loss of （） from an air compressor could lead to an overheated air discharge and possibly an explosion in the pipelines leading to the air reservoir.

单项选择题 The joint face between the cylinder cover and the liner is arranged （）the combustion process as possible.