What is the mechanism by which carbon dioxide heats Earth? What is the source of most of the carbon dioxide in the atmosphere? What is the source of the increase of carbon dioxide in the atmosphere? What is the increase in the concentration of carbon dioxide in the atmosphere?
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Scientists think that the rise in global temperature during the last one hundred years is due to an increase of carbon dioxide in the atmosphere. Which question would best help scientists assess the claim that humans are responsible for the rising global temperature?
Possibilities:
- What is the mechanism by which carbon dioxide heats Earth?
- What is the source of most of the carbon dioxide in the atmosphere?
- What is the source of the increase of carbon dioxide in the atmosphere?
- What is the increase in the concentration of carbon dioxide in the atmosphere?

What is the source of the increase of carbon dioxide in the atmosphere?