某同学家室内的电灯均正常工作，当他把“220V  8W”的台灯插头插入插座后，闭合台灯开关，室内电灯全部熄灭，发生这一现象的原因可能是                                                                                                                                                                                                                                              

A．插座处短路   B．台灯插头处短路   C．台灯开关处短路   D．台灯灯头处短路