单项选择题
Spring tides are tides that（）.
A.have lows lower than normal and highs higher than normal B.have lows higher than normal and highs lower than normal C.are unpredictable D.occur in the spring of the year
单项选择题 River currents tend to（）.
单项选择题 Priming of the tides occurs（）.
单项选择题 Neap tides occur when the（）.
