Answer:
The correct answer would be the concentration level of carbon dioxide.
Step-by-step explanation:
There are three major factors or say limiting factors that affect the photosynthesis rate. These factors are light intensity, carbon dioxide concentration, and temperature.
Increase or decrease in any of these 3 limiting factors will directly affect the photosynthesis rate taking place.
Increasing carbon dioxide concentration will increase photosynthesis up to a particular limit while a decrease in carbon dioxide concentration will decrease the photosynthesis rate.
Thus, the correct answer is the concentration of carbon dioxide,