During the dark reaction of photosynthesis:

Explanation

The dark reactions occur in the stroma of the chloroplast and are also known as the Calvin cycle. In this stage, the enzyme RuBisCO helps combine carbon dioxide with ribulose-1,5-bisphosphate to form 3-phosphoglycerate, which is then converted into glucose and other carbohydrates using the ATP and NADPH produced during the light reactions. The other options are incorrect because chlorophyll activation and photolysis occur during the light reaction, and the breakdown of six-carbon sugars into three-carbon sugars is part of cellular respiration, not photosynthesis. Therefore, the correct answer is that carbon dioxide is reduced to organic compounds during the dark reaction.