Pyramid of energy is ecological pyramid that gives graphic representation of amount of energy trapped by different trophic levels per unit area. It is always upright because during transfer of energy from one trophic level to the next a lot of wastage occurs in feeding, digestion, assimilation and respiration i.e metabolism at each trophic level. Hence, organisms of each trophic level have more energy than each succeeding trophic level and less energy than organisms at previous trophic level. Thus, the correct answer is option D.