电暖器接入电路时与其他家用电器的连接方式是 ▲ （选填“串联”或“并联”）.某家庭电路中电能表的示数为，若一个“220V 800W”的电暖器单独
Recently, one of my best friends, whom I've shared just about everything with since childhood, spent the weekend with me．Since I moved to a new town several years ago, we’ve both always looked for
一横波在某一时刻的图象如图所示，其波速为5m/s，其上有一质点A，下列说法正确的是 A．此波的频率为5Hz B．质点A的按振幅为0C．此波的波
如图，AB是⊙O的直径，AC是弦，D是AC的中点，若OD＝4，则BC＝_______．
工业上可以利用氟硅酸、碳酸氢铵制备冰晶石（Na3AlF6），其工艺如下： 请回答下列问题： （1）反应①中生成的无色气体A是
10.Here _____ a new pair of shoes for you. A. is B. are C. have D. Has
—Sorry, I made a mistake again. — Practice more and you’ll succeed. A. Never mind B. Certainly not C. Not at all
的夹角为
则
在
上的投影为 