(If the work is about food chains)
A. The transfer of biomass when one organism eats another is basically energy that is transferred. The energy is passed between organisms as one organism eats the other. Food chains starts with producers. This energy is used during life processes such as metabolism, respiration, etc.
B. The energy that is not transferred will probably be lost through metabolic processes as heat.
C. There are typically fewer organisms at the top because they are mostly the predators. Meaning that the organisms below them is their source of energy and the organisms below are the second top layer’s source of energy and so on.