How are all the species in a food chain similar to links in a metal chain

They're similar because in a food chain, if you take away one animal the whole chain breaks, and with a metal chain, if you take away one link, the entire chain falls apart.

one thousand and one nights, also known as arabian nights is a collection of stories whose basic structure is that of embedded narrative. this technique refers to a main story which works as the common frame - or framing narrative - for the other stories, and then this series of stories which are connected to the main one. this technique can also be referred to as a story within a story. the stories stem from the original tale, some begin and end on their own, some are connected to the previous or following one, by means of questions that are answered in the subsequent tale, or characters which reappear.

this answer to this question is c. allegory

why?

stories with allegories have a hidden symbolic meaning with a theme. the hidden meaning can be political, or other real life problems.