题目

  Mary sits in front of Kate, so Kate is _____ Mary.         A. over    B. beside      C. behind      D. under 答案：C图中所给出的杠杆中，属于费力杠杆的是（　　）A．        撬杠B．      抽水机手柄C．         裁纸刀D．       缝纫机脚踏板