Which of the following is not a limitation of ecological pyramids?

The pyramid of energy is always upright and can never be inverted because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step.

Limitations of ecological pyramids are:

(a) Any species belonging to two or more trophic levels cannot be represented by ecological pyramids.

(b) Ecological pyramids assume simple food chain (which almost never exists in nature).

(c) Ecological pyramids do not accommodate food web.

(d) Saprophytes are not given any place in ecological pyramids.