Answer:
Grass
Step-by-step explanation:
A producer or autotroph is an organism that produces its own food. These include plants, algae, and some bacteria. They convert carbon dioxide, water, and light energy from the sun into glucose, a type of sugar that provides energy, in the process of photosynthesis.
The organisms we are given are grass, prairie dog, ferret, and fox. The only plant is grass. Prairie dogs, ferrets, and foxes are all consumers, and depend on other organisms (plants, grass, leaves, or other animals for meat) for food.
Therefore, the producer in this list is grass.