属于黄土高原环境脆弱表现的是[ ]
A、地下矿产多，地面开矿多
B、处于平原向山地过渡的地区
C、土壤遭到侵蚀后，难以恢复原来的肥力
D、水旱灾害频繁
CD
Suppose you tried to lift a 100-pound rock two feet, you______more work than if you______ it one feet.
A．would do...lifted
B．did...lifted
C．will do...will lift
D．would do...will lift
蛋白质生物价
