5.A condenser is used to collect and store e_________.

4.In the 18th and 19th centuries scientists made many important _________(发现).

3.Setting up a car factory here can help develop the e_________in this area.

2.Everything has its own advantages and d_________.

1.It's _________(不必要)to spend so much money on clothes.

19.轮子 _________　　　　　　　　　 20.结论_________

17.怀疑_________　　　　　　　　　　 18.残酷的_________

15.洗发精_________　　　　　　　　　 16.药物_________

13.丝带 _________　　　　　　　　　 14.解释,说明_________

11.锋利的_________　　　　　　　　　 12.扎牢,拴紧_________