一、根据句意及中文提示写出所缺单词的完全形式，
1. Chinese _________ (文明) is one of the oldest in the world.
2. John is collecting _________ (材料) for a report.
3. It has been many years since Mount Vesuvius last _________ (爆发).
4. You can’t stop smoking at once; you need to give it up _________ (逐渐)
