调节系统静态性曲线在空负荷区附近的曲线（）。
A.呈水平段
B.陡一些
C.斜率小些
参考答案：B
After Mary and Jane covered 25 kilometers that day, their legs under them _____.
[ ]
A. gave in
B. gave off
C. gave out
D. gave away
过原点作曲线y＝lnx的切线，求此切线与y＝lnx和x轴围成的平面图形的面积。
