Plankton, term- zooplankton:)
Hope this helped
I think the answer is D.
<span>Densely populated areas with sparse vegetation. </span>
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.
Answer:
Fermentation allows production of energy without oxygen. This is helpful for conserving oxygen.
Explanation: