选择电动机功率的主要依据是( )。
A．功率因数
B．负载转矩
C．启动电流
D．电压
参考答案：B
Russ and Earl were auto mechanics _____ the same pay, but Earl had more ambition. [ ]
A. earned
B. to have earned
C. to earn
D. earning
下图中所示近地面大气的热量主要来自
A．A
B．B
C．C
D．D
