用所给单词的适当形式填空。

1. My best friend is from __________ (Japanese).

2. This is the __________ (begin) of the garden tour.

3. The koalas often sleep during the day and eat __________ (leaf) at night.

4. Don't play football in the street. It's __________ (danger).

5. Are they __________ (friend) to you?

抗氧剂对聚合物由于氧化降解所产生的过氧化物分解成非游离基的稳定化合物。