To answer this we need to analyze each available option
A. food chain. This is the simplest way to represent how energy passes among organisms, it is reductionist and information is lost however is the most simple way to picture this, therefore this is the correct answer.
B. energy pyramid. This diagram certainly is simple, however, has a bigger amount of information and can be done as complex as one wishes so even when this applies it has restrictions.
C. trophic level. This cannot be as trophic level refers only to the position of the organism either be in the chain, pyramid, or web.