坡积土层
参考答案：
雨雪水流的地质作用将高处岩石风化产物缓慢地洗刷剥蚀，顺着斜坡向下逐渐移动、沉积在较平缓的山坡上而形成沉积物。
It was not until she arrived at the classroom she realized she had forgotten her coursebook.
A．and she realized
B．which she realized
C．then she realized
D．that she realized
以下几种材料中，属于优质碳素结构钢的是（）。
A.Q235A
B.40
C.T8
D.T12A
