A complex feeding relationship between organisms in a habitat that involves transfer of energy in form of food is

In ecology, organisms in a habitat are connected through feeding relationships. A food chain is a simple, linear sequence showing how energy passes from one organism to the next, for example: grass to grasshopper to frog to snake to hawk. Each organism feeds on the one before it.

However, most ecosystems are far more complicated than a single chain. A grasshopper may be eaten by both frogs and birds; a frog may eat insects other than grasshoppers; a hawk may eat snakes, mice, and birds. When multiple food chains in a habitat overlap and interconnect, the result is a food web. A food web captures the complex feeding relationships among all the organisms in the habitat, showing how energy in the form of food is transferred through many interlinked pathways.

A pyramid of numbers shows how many organisms exist at each trophic level, while a pyramid of energy shows the amount of energy available at each trophic level. Neither of these describes a feeding relationship between organisms. They are graphical representations of quantity, not of who eats whom.

The key phrase in the question is "complex feeding relationship ... that involves transfer of energy in form of food." Only a food web fits this description, because it is the model that represents the full network of interconnected feeding relationships within a habitat.