Answer:
i think it's D
Explanation:
my bad if u get it wrong or anything
An organism that can live in only one particular environment or that can survive on only one type of food would be called a specialist.
Maybe water Ian nothing B because it’s not C
I would say energy myself, and this is because energy plays a key role in all of these. With trophic levels energy is being transferred amongst the levels. Food chain's is a map of how the energy is passed along the chain. Food web is a web of how energy is transferred, and this is why I would say energy is a keyword.