液压传动是利用（）递能量的传动机构。
参考答案：工作液体传
—It's a fine day today. Shall we go swimming?
—_______ But we need to be home before six o'clock. [ ]
A. Have a nice time!
B. Not at all.
C. You are right.
D. Good idea!
正常老人白天排尿多少次( )。
A．2-4次
B．3-5次
C．6次
D．7次
