Answer:
A. The Sun
Step-by-step explanation:
The farther down the food web or food chain you go, the less energy is transferred from one organism to the next. This means that by one organism consuming the other, the one doing the consuming will receive less energy than the one that it had just consumed had from whatever it ate.
Because the sun is the basis on all energy, and producers get their energy from the sun, it carries the most amount of energy.