The correct answer is A.

In the pyramid of energy, the most energy is always found among primary producers. Primary producers are either plants or photosynthetic bacteria. Energy is lost with each level in the pyramid as most of the energy is utilized for maintenance of the organism and things such as movement and warmth. Only a fraction of the energy produced becomes new tissue, which can be harvested by the next level up in the pyramid. This should remind you of some general chemistry principles that with any exchange of energy, some is lost. Primary consumers are herbivores while secondary consumers are typically carnivores, which ingest the herbivores, and tertiary consumers will prey upon the secondary consumers.