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？
