Answer: The correct answer is -
Decrease in the rate of photosynthesis that is formation of carbohydrate (glucose) will be reduced.
Carbon dioxide (CO2) is one of the essential reactants in the process of formation of food (photosynthesis) in plants.
Photosynthesis is a process of formation of food (glucose) in green plants and algae using CO2 and H2O (water) in the presence of sunlight.
If all the available carbon dioxide is used up by a plant, the process of photosynthesis will be affected significantly, which will cause a decline in the formation of carbohydrate (glucose) in the plant.