The energy available to consumers determined by subtracting the energy used by plants from the total energy transformed by the process of photosynthesis.

The question is incomplete as it does not have the option which are:

A. Gross primary productivity

B. Net primary productivity

Net primary productivity

Explanation:

In a food chain, the producers are present at the bottom of the trophic level which absorbs the sunlight and converts the energy into other molecules called glucose by photosynthesis.

This glucose is then either used by the producers to form energy molecules called ATP for its metabolism or it could either store it in the form of the starch.

The energy which is absorbed by the producers per unit area in a unit time refers to the Gross primary productivity and the energy which is stored after the plant utilizes the glucose molecule to produce energy is known as the net primary productivity.

In other terms, the energy which is stored after energy used for metabolism from subtracting gross primary productivity is known as Net primary productivity.

Therefore, it is clear that only net primary productivity is utilized by the consumers and thus is the correct answer.

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.