单项选择题
A.hydraulic current
B.rectilinear current
C.rotary current
D.harmonic current
单项选择题 A survival craft being used to pick up a person who has fallen overboard from a ship should approach the person（）.
单项选择题 A sufficient amount of chain must be veered when anchoring a vessel to ensure（）.
单项选择题 A strong，often violent，northerly wind occurring on the Pacific coast of Mexico，particularly during the colder months，is called（）.