a) 1. Environment
2. Endangered species
3. Greenhouse effect
4. Threaten
5. Pollution
6. Global warming
7. Climate
8. Pollute
9. Recycle
b) 1. Threaten
2. Greenhouse effect
3. Environment
4. Pollution
5. Global warming, climate
6. Recycle
7. Pollute
8. Endangered species
