Explain the principles of a food chain​

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. In a food chain, each organism occupies a different trophic level, defined by how many energy transfers separate it from the basic input of the chain.

Explanation:

b.

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.