What specific trophic role do red foxes and black bears fulfill in the North American grassland and forest food web model?

Which of the following represents a correctly ordered terrestrial food chain?

With reference to food chains in an ecosystem, consider the following statements: I. The number of trophic levels in a food chain is limited by the amount of energy available at the producer level. II. Detritus food chains transfer a significant portion of energy as heat during decomposition processes. III. Solar energy is the ultimate source of energy for both grazing and detritus food chains. Which of the statements given above are correct?