造成螺杆泵密封泄漏的原因是()。
A、填料或密封圈损坏
B、填料材质合格
C、油品粘度过大
D、螺杆与泵套磨损
参考答案:A
Mr Smith is a strict but good teacher, _______cares about both our study and life.
A.one who
B.whoever
C.the one
D.the person
开放式基金的赎回费率不得超过赎回金额的( )。
A.2%
B.3%
C.4%
D.5%