用适当的介词填空。

1. Danny isn't ____ school today, and he has been ____ for three weeks.

2. I'm going to play basketball on the playground ____ school.

3. There are plenty      flowers in the garden.

4. What shall we write      our poster?

5. Let's make a poster ____ drinking.

6. Drinking too much is also bad ____ your health.

7. I have an idea ____ your plan.

华南虎（又称中国虎）是我国特有的亚种，全球只剩下不到100只，在野外生存的华南虎可能只有10到30只。影响它们数量的首要原因是人虎冲突。近代，人口迅速增长，导致华南虎的栖息地碎裂化、岛屿化，很难满足华南虎的生存和繁殖的要求。第二个原因就是华南虎的很多食物是人类的经济动物，当人们的猎杀使这些动物的种群密度降低到一定程度时，华南虎已经很难生存。

如何解释当栖息地碎裂化、岛屿化时，华南虎的生存和繁殖就变得异常困难？

①（）

②（）