Answer the following question given this paragraph: 

Most scientists agree that global warming is caused by more carbon dioxide in the atmosphere (see Figure below ). This increases the greenhouse effect. There is more carbon dioxide mainly because of the burning of fossil fuels. Destroying forests is another cause. With fewer forests, less carbon dioxide is removed from the atmosphere by photosynthesis.


Q: The abundance of this substance in the atmosphere is what most scientist agree that is causing global warming?

 Choices:

- argon

- iron oxide

- liquid dioxide

- carbon dioxide

A:
carbon dioxide
