Answer the following question given this paragraph: 

The atmosphere contains small amounts of carbon dioxide. Climatologists have found that humans are putting a lot of extra carbon dioxide into the atmosphere. This is mostly from burning fossil fuels. The extra carbon dioxide traps heat from the Sun. Trapped heat causes the atmosphere to heat up. We call this global warming ( Figure below ).


Q: Which gas is responsible for global warming?

 Choices:

- oxygen

- hydrocarbons

- ozone

- carbon dioxide

A:
carbon dioxide
