单项选择题
Neap tides occur only（）.
A.at a new or full Moon B.when the Sun，Moon，and Earth are in line C.at approximately 28-day intervals D.when the Moon is at quadrature
单项选择题 Neap tides occur（）.
单项选择题 In which month will the equatorial counter current be strongest? （）
单项选择题 In mid-ocean，the characteristics of a wave are determined by three factors. What is NOT one of these factors?（）
