改变载波频率可改变PWM逆变器的()
A. 开关频率
B. 输出信号波频率
C. 调制信号波频率
D. 一个周期内的pWM脉冲数
How does the "observer" carry out his assessment?
A. By wandering around the school and observing the teacher in a casual way.
By attending and evaluating the teacher's class in a formal way.
What does "dig into" mean here?
A. The lable rubs against the body in a painful way.
B. The lable pushes hard into the body and it makes Bradley bleed.
1992年10月,中共十四大在北京举行。报告明确指出,我国经济体制改革的目标是()。
A. 建立社会主义市场经济体制
B. 加强国家宏观调控
C. 改革开放
D. 国民生产总值比1980年翻一番