(____)I don't know.
(____)Where is my pencil?
(____)Li Hua, Where's your pencil?
(____)There it is.
(____)Danny, where is my pencil? Can you see it?(你看见它了吗?)
____+____=____ ____+____=____
____-____=____ ____-____=____
在如图的列联表中,类Ⅰ中类B所占的比例为( )
在如图所示的电路中,电源电压保持不变,灯泡L1或L2中有一个发生了短路故障,当开关S闭合时,下列现象中不可能出现的是( )