Choose the correct options to complete the definitions

1. [Waste|Pollution]
   is the damage caused to water, air, etc. by harmful substances or waste.
2. [Deforestation|Degradation]
   is the cutting down of trees in a large area or the destruction of forests by people.
3. [Litter|Pollution]
   is small pieces of rubbish that have been left lying on the ground in public places.
4. [Existence|Extinction]
   is a situation in which something no longer exists.
5. [To litter|To waste]
   means to use something without care or thought.
6. [Global warming|Carbon dioxide]
   is a gradual increase in world temperatures.