题目

The weather turned out to be fine yesterday. You ________ the trouble to carry your raincoat with you.   A. should have taken                                   B. mustn’t have taken   C. could have taken                                     D. needn’t have taken  答案：D某手电筒闭合开关后不发光，请写出灯泡不亮的两种可能原因．（1）在电路某处可能发生的情景是：__________________________________________；（2）在电源处可能发生的情景是：____________________________________________。