The correct option is A Loss of energy at each trophic level
Loss of energy at each trophic level is the reason which limits the number of trophic levels in a food chain. Ten percent law states that "when energy is transferred from one trophic level to the other, only 10% energy from the organic matter is passed on". As a result of this, energy available at the last trophic level becomes very less to support any further trophic level.