单项选择题
The flood stream here is at an average rate of 0.8（）.
A.cables B.miles C.kilometers D.knot
单项选择题 The construction portfolio may be included as part of the ship（）.
单项选择题 The circular steel structure installed around the propeller of a towboat is the（）.
单项选择题 The bow thruster generally is ineffective at（）.
