Final answer:
The energy from light is gathered on the thylakoids and used to synthesize CO2 for release by the carboxysome. Therefore, the correct option is d.
Step-by-step explanation:
The best-supported claim about the relationship between thylakoids and the carboxysome is that energy from light is gathered on the thylakoids and used to synthesize CO2 for release by the carboxysome. Thylakoids, which are part of the chloroplast, are responsible for capturing light energy during photosynthesis. This energy is then used in the Calvin cycle, which takes place in the stroma, to produce glucose molecules, some of which are later broken down to release CO2 by the carboxysome. Therefore, the correct option is d.