Final answer:
The true statement about trophic levels is that carnivores occupy a higher trophic level than herbivores. Energy flows from the first trophic level of autotrophs up to herbivores and then to carnivores, and decomposers break down matter from all levels but are not at the first trophic level.
Step-by-step explanation:
Trophic Levels in an Ecosystem
The question about trophic levels in an ecosystem relates to the way energy flows through different groups of organisms, from producers to various levels of consumers. Looking at the options provided, the true statement about trophic levels is that carnivores occupy a higher trophic level than herbivores. In a typical energy pyramid, energy flows from the first level (autotrophs or producers), up to herbivores (second level), and then to carnivores (third level or higher). Decomposers, which consume organic wastes and dead organisms, can be said to feed off multiple trophic levels as they break down matter from all levels after death, but they are not placed at the bottom or first trophic level as producers are.
Regarding the given statements: Energy does not flow from herbivores to autotrophs; it flows from autotrophs to herbivores. Decomposers are not considered at the first trophic level; instead, they break down matter from all trophic levels. Primary consumers are not always omnivores; they can be strictly herbivores as well. Thus, the correct answer to the question is that carnivores occupy a higher trophic level than herbivores.