A. osmosis because no energy is needed to carry it out
Between every food chain from one animal to another there is 90% energy loss so if a herbivore eats a plant, it will only get 10 joules of energy. and if a carnivore eats the herbivore then it will only get 1 joules of energy. so in every food eaten, there is 90% energy loss.
Because good researchers rely on first hand account or better said primary evidence. The reason why they rely on primary evidence is because it is usually the most reliable. Much more so than secondary or even tertiary evidence. This enables them to understand the history of a certain topic better.