Explanation:

- Let’s break this down. Autotrophs are organisms that can make their own food, usually by photosynthesis.

- Option 1: Protozoa—these are single-celled organisms, but they don’t make their own food. They’re more like tiny animals, eating other things for energy.

- Option 2: Animals—definitely not autotrophs. Animals get energy by eating plants, other animals, or both.

- Option 3: Viruses—not even really alive. They can’t make food, can’t grow, can’t do much on their own at all.

- Option 4: Green plants— this is the one. Green plants are classic autotrophs. They use sunlight, water, and CO2 to make their own glucose through photosynthesis.