题目

We have ______ at 7 in the morning. A . breakfast B . lunch C . dinner D . dessert 答案：A11．两灯上分别标有“6V、3W”和“6V、6W”字样，当两灯串联时电源电压为9V，总功率为4.5W．当两灯并联时，干路电流为1.5A．