根据括号内的汉语提示完成句子，每空一词。

1. We aim ______ (提供) them with nice homes.

2. People have come to realize the ______ (重要) of protecting environment.

3. With the increase in population and the ______ (发展) of industry, litter is everywhere.

4. I often eat fresh fruit and vegetables ______ (代替) of chips and chocolate.

5. I think it is important to master computer ______ (技术) now.

6. I can't go shopping in a big store ______ (除非) I travel for a couple of hours.