The answer is C. Primary consumers eat plants and as we can see on the food chain, the arrows represent the transfer of energy. The energy transfer is shown to be going between the Grass and Cactus and to the Rabbit and Grasshopper.
Looking at the Food Web Diagram, we can see that the rabbit and grasshopper are the main herbivores. Or another way to look at it is: which are the primary consumers of the producers (plants)?? The cactus and grass are the plant producers in this web, thus the main consumers of these producers are the herbivores known as primary consumers. According to the diagram, those could only be the rabbit and grasshopper. If a question asked what are the secondary consumers, those would be the carnivores above them. But the final answer is therefore: C) rabbit and grasshopper.
