The concentration of carbon dioxide in parts per million (ppm) was measured for a closed container in several situations. Which of the following data collected would demonstrate the action of photosynthesis? 1) When multiple plants were put in the container, carbon dioxide concentration never got above 1,000 ppm.

2) When carbon dioxide concentration went from 800 to 1,000 ppm the temperature in the container went up.

3) Plants in the container kept in darkness did not lower the concentration of carbon dioxide below 800 ppm.

4) When the container included a plant exposed to light, carbon dioxide concentration went from 800 to 600 ppm.