如果存在齿轮偏心,则齿轮啮合频率仅存在()时。
A.上边带频
B.下边带频
C.侧边带频
D.中边带频
参考答案:B
—Is the man over there Mr. Brown?
—It __________ be him, He's much shorter. [ ]
A. must
B. can't
C. needn't
D. may
按中小企业客户对中国人民银行的贡献度或可能提供的贡献,可以分为哪几类?