Photosynthesis consists of two primary steps: light reactions and the Calvin cycle (also known as the dark reactions). Therefore, the correct answer from your options is A: light reactions in Calvin cycle.
- Light reactions: These occur in the thylakoid membranes of the chloroplasts and convert light energy into chemical energy (ATP and NADPH).
- Calvin cycle: This takes place in the stroma of the chloroplasts and uses the ATP and NADPH produced in the light reactions to fix carbon dioxide and produce glucose.