Final answer:
A food chain shows how energy moves through a population, representing a linear sequence of organisms where nutrients and energy are passed from one organism to another.
Step-by-step explanation:
The statement that is true about a food chain is a) It is how energy moves through a population. A food chain is a sequence of organisms through which nutrients and energy pass as one organism eats another, starting with producers and ending with decomposers. The statement that a food chain contains only one population for each trophic level is not accurate, as multiple species can occupy the same trophic level. Also, the statement about food moving through a population is more reflective of food webs that show the complex interactions between different species.