单项选择题 The film of oil between the rings and the liner is not only essential for the lubrication but also plays an important part in achieving （）.

单项选择题 The figure that the volume of air at BDC is divided by the volume of air at TDC is termed as（）.

单项选择题 The external circumference of a pair of main bearing shells is slightly larger than that of the bore of the housing which receives themThe difference is termed （）.