调节系统动态特性试验的目的是测取电负荷时转速飞升曲线,以准确评价过渡过程的品质。
参考答案:对
Jim is standing at the corner. He ______ for the bus. [ ]
A. was waiting
B. is waiting
C. waits
D. waited
乙炔与空气能组成爆炸性混合物,在空气中含有()体积的乙炔,点火时即能引起爆炸。
A、3%~81%
B、13%~81%
C、9%~81%
D、19%~81%