Answer: D. A decrease in its sugar production.
Explanation: Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in the form of organic molecules, such as glucose. Carbon dioxide is one of the key reactants required for this process, and if the chloroplast uses up all the available carbon dioxide, the rate of photosynthesis will decrease. This is because without enough carbon dioxide, the Calvin cycle, which is the part of photosynthesis that produces glucose, will slow down. As a result, there will be a decrease in the production of sugar in the chloroplast.