Answer:
The correct option is DECREASED LEVELS OF CARBON DIOXIDE.
Step-by-step explanation:
The major factors affecting photosynthesis rate are light intensity, carbon dioxide concentration and temperature. Increase or decrease in any of these three factors will directly affect the rate at which photosynthesis takes place. Increase concentration of carbon dioxide will generally increase photosynthesis while a decrease in its concentration will reduce the rate at which photosynthesis takes place.