小儿肺活量为()。
A.30~50ml/kg
B.50~70ml/kg
C.70~90ml/kg
D.90~110ml/kg
E.110~130ml/kg
参考答案:B
We all hope that our head teacher is both strict _____ us and friendly _____ us. [ ]
A. in, to
B. in, for
C. with, to
D. with, for
简述轴承流体动压润滑的机理。