曳引绳的长度应保证电梯在顶层端站平层时,对重与液压缓冲器间应有()mm的间隙。
A.150~450
B.50~350
C.250~450
D.350~450
参考答案:A
-What’s the trouble?
-I am having trouble who has taken my book. [ ]
A. finding
B. looking for
C. finding out
D. looking up
维持内脏位置相对恒定的脏是()。
A.心
B.肝
C.脾
D.肺
E.肾