单项选择题
The term PROLONGED BLAST refers to（）.
A.a blast of from five to seven seconds' duration B.a blast of from five to six seconds' duration C.a blast of from four to six seconds' duration D.a blast of from six to seven seconds' duration
单项选择题 The ship will be（）demurrage soon.
单项选择题 The ship is now down（）head.
单项选择题 The ship is not very stable，please（）when making a turn.
