Explanation:

- Autotrophs are organisms that can use carbon dioxide (CO2) as their primary carbon source, typically through photosynthesis or chemosynthesis.

- Correct Answer: Autotrophs

- Heterotrophs cannot produce their own food and rely on organic compounds from other organisms.

- Parasites feed on a host organism, deriving nutrition at the host's expense.

- Decomposers break down dead or decaying organisms, thus recycling nutrients back into the ecosystem.