单项选择题
A.They occur only at quadrature
B.They occur when the Moon is nearest the Earth
C.They cause diurnal tides to become mixed
D.They have a decreased range from normal
单项选择题 Which current would you encounter on a direct passage from southern Africa to Argentina，South America（）.
单项选择题 Which current would you encounter on a direct passage from London，England，to Capetown，South Africa（）.
单项选择题 Which current is responsible for the movement of icebergs into the North Atlantic shipping lanes（）.