造成黄土高原水土流失严重的人为原因,主要是[ ]
A.陡坡地退耕还林还草
B.植被遭到人为破坏
C.黄土土质疏松
D.降水集中,多暴雨
答案:B
—What can I do famous?
—You must study hard.[ ]
A. become
B. to become
C. became
D. becoming
轴向推力有什么危害?