船舶（）至少有一个救生圈应装有可浮救生索，索长（）米。
A、驾驶台；30
B、每舷；30
C、船首；30
参考答案：B
I can't leave. She told me that I _____ stay here until she comes back. [ ]
A. can
B. must
C. will
D. may
在低压配电箱上的工作，应至少由（）人共同进行。
A.4
B.1
C.3
D.2
