National flag should not be （）up.

单项选择题You should keep national flag（）.

A.flying
B.flew
C.flown
D.flies

单项选择题You should slack the mooring lines （）when the wind is big.

A. at the same time
B. on time
C. in time
D. at times

单项选择题We must （）to inspect the problems about the safety of fire prevention.

A.prepares
B.preparing
C.prepared
D.prepare

单项选择题When you keep a gangway watch, you should （）the mooring lines according to the rise and fall of the tide.

A.adjusted
B.adjusting
C.adjusts
D.adjust

单项选择题Lower gangway into place and （）safety net.

A.fast
B.make fast
C.fasten
D.fastened