Final answer:
Food chains typically consist of only three or four steps due to the fact that only approximately 10% of the energy at one trophic level is transferred to the next level, with the rest being lost as heat or used for metabolic processes.
Step-by-step explanation:
Food chains generally consist of only three or four steps because 10% energy is available to the consumers. The correct answer to the question is Option A: 10% energy is available to the consumers. As energy is transferred along a food chain, energy is lost as heat at each trophic level, and because only about 10% of the energy at one level is stored in the body tissues at the next level, the energy that can be passed on decreases significantly with each step.
The majority of the energy is used by the organism for metabolic processes or released into the environment as heat. This loss of energy explains why there are rarely more than four trophic levels in a food chain or web. It is because of these energy constraints that the length of food chains is typically short.