当海面由高潮下降到低潮的过程，称为（）。
A.高潮
B.低潮
C.涨潮
D.落
参考答案：D
_____ days went by, he didn't succeed in anything he had planned. [ ]
A. With
B. When
C. As
D. While
一般的( )的规格为长2 700～3 000 mm，宽500～800 mm，厚90～120 mm。
A．加气混凝土条板 B．碳化石灰板C．增强石膏空心板 D．复合板
g he had planned. [ ]