单项选择题
Some ships have special duties, such as（）（驳船）.
A. liquid cargo ships B. general cargo ships C. barges D. tugs
单项选择题 （）（滚装船）have doors at the bow or stern.
单项选择题 （）(送出) two head lines ,one from each side.
单项选择题 We must（）(后移)one metre.
