The summer of 1998 was one of the hottest summer seasons on record. Carbon dioxide gas from cars and industry is a product of burning that produces heat. Carbon dioxide in the upper atmosphere reflects heat radiated from Earth's surface. Radiation on Earth's surface is increasing because of a hole in the ozone layer
I gave my students this multiple choice question: Many scientists accept the theory that excess emission of carbon dioxide from cars and industry causes a layer of gas in the upper atmosphere that traps heat. This, in turn, causes the average temperature on Earth to rise. Which of the following observations supports that theory?

Only one answer is correct among these 4 choices:
- The summer of 1998 was one of the hottest summer seasons on record.
- Carbon dioxide gas from cars and industry is a product of burning that produces heat.
- Carbon dioxide in the upper atmosphere reflects heat radiated from Earth's surface.
- Radiation on Earth's surface is increasing because of a hole in the ozone layer

Could you tell me which one is correct?

Carbon dioxide in the upper atmosphere reflects heat radiated from Earth's surface.