直流电动机试运时，磁场电阻器应放在（）位置，直流发电机则应放在（）位置。
参考答案：最小；最大
The well-known Garub Site, unearthed in 1997, shows that man had made living there as early as 5,000 years ago.
A．human had lived
B．humans had lived
C．human being lived
D．human beings lived
硫池上方的蒸汽喷射器起什么作用？
