电力晶体管的缺点是（）。
A、功率容量小
B、必须具备专门的强迫换流电路
C、具有线性放大特性
D、易受二次击穿而损坏
参考答案：D
甲乙两人合作2小时可以完成一项工作．如果由甲单独完成需要6小时，那么由乙单独完成的工作效率是甲单独完成的工作效率的______倍．
根据句意及首字母或汉语提示，补全单词。
小题1:Mrs. Green often goes to the m__________ to buy some vegetables.
小题2:Tom is very sad. His little dog has been d___________.
小题3:It’s impolite to d__________ others while they are sleeping.
小题4:China has developed __________ (迅速地) in the past ten years.
小题5:__________ (虽然) there were many difficulties, they didn’t give up.
