Correct representation of trophic levels in a food chain is shown in figure A.

The population will decrease as we move from bottom to top of a food chain. The producers will be the highest in number in a food chain because there have to be more food producers than consumers, to sustain life on earth. The top position is mostly taken by carnivorous animals (tertiary consumers), omnivores being the secondary consumers and herbivores being the primary consumers.

A food chain always represents a unidirectional flow of energy from one trophic level to another. Each level in the pyramid represents our level in the food chain. Each level of consumers above the producers has fewer individuals because there is less energy available.