什么是空压机的排气量？
参考答案：
空压机是指空压机最末级排气端在单位时间内排出的气体量，再换算成吸气状态下（第一级）的空气容积。
Schools across China are expected to hire 50,000 college graduates this year as short-term teachers, almost
three times the number hired last year, _____ reduce unemployment pressures. [ ]
A. help
B. to have helped
C. to help
D. having helped
通电导线所受安培力的方向与磁场方向、电流方向的关系，下列图示正确的是 [ ]
A．
B．
C．
D．
