Which of the following is true about energy in ecosystems? a. The total available energy at the top trophic level is equal to the sunlight energy that enters the ecosystem b. The total available energy increases with each trophic level c. The total available energy is determined by the number of tertiary consumers (top predators) d. The total energy in the ecosystem is conserved, but some available energy is lot as heat or used to do work at each trophic level