根据汉语意思或首字母提示.用适当的词补全句子.

1. Although it was expensive, we _____ (决定) to buy it.

2. Who _____ (发现) America first?

3. I like eating _____ (脆的) cookies. They are hard,dry and easily broken.

4. I met her by a _____ in a crowded bus.

5. A c _____ means a hundred years.

生石灰的等级共分为三级。