单项选择题
When the wave period and the apparent rolling period are the same（）.
A.synchronous rolling occurs B.roll period decreases C.roll period increases D.roll amplitude is dampened
单项选择题 In the Northern hemisphere northerly winds may cause temperature（）.
单项选择题 Which of the following is not a form of precipitation?（）
单项选择题 Waves formed by the wind blowing far away are known as（）.
