单项选择题
A.in order to
B.because of
C.so that
D.so as to
单项选择题 The film of oil between the rings and the liner is not only essential for the lubrication but also （） achieving a gas seal.
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（）.