A. What are they doing now?
B. Where are they?
C. Do you see any animals?
Amy:____
Mike: Yes, I see two ducks.
Mike: They are in the river
Mike: They're swimming.
凸透镜甲的焦距为10cm,凸透镜乙的焦距为20cm,把同一个物体分别放在甲、乙前25cm处,则通过两个凸透镜都能在光屏上成清晰的像,下列说法正确的是 ( )
在原子核中,带正电的粒子是( )
关于植物呼吸作用的叙述,正确的是 ( )
复数z=2i-1,则图中表示z的共轭复数的点是( )