单项选择题 In some parts of the world there is often a slight fall in tide during the middle of the high water period. The effect is to create a longer period of stand at higher water. This special feature is called a(n)（）.

单项选择题 In shallow water，waves that are too steep to be stable，causing the crests to move forward faster than the rest of the wave，are called（）.

单项选择题 In most cases，the direction of the apparent wind lies between the bow and（）.