题目

 Why not stay at home      the road is so slippery after the heavy snow?    A. since that      B. now that       C. then that      D. after that 答案：B在下列情况中，机械能守恒的是（ ）A．物体在斜面上匀速下滑B．石头从手中抛出后的运动（不计空气阻力）C．子弹射穿木块D．在空气中匀速下落的降落伞