Answer the following question given this paragraph: 

Efforts to reduce future global warming mainly involve energy use. We need to use less energy, for example, by driving more fuel-efficient cars. We also need to switch to energy sources that produce less carbon dioxide, such as solar and wind energy. At the same time, we can increase the amount of carbon dioxide that is removed from air. We can stop destroying forests and plant new ones.


Q: Reducing the production of what gas, or removing it from the air, are practices that could reduce global warming?

 Choices:

- helium

- hydrogen

- oxygen

- carbon dioxide

A:
carbon dioxide
