Answer:
C. Oxygen
Explanation:
Most, if not all living things use oxygen in some shape or form. While Helium is the most abundant element, it is asking for living things, in which oxygen is a vital building block in maintaining life. Without oxygen, most animal species and humans would die.
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They turn to water right-
My guess is that fat-soluble toxins that may occur in freshwater ecosystems would most affect apex species in these ecosystems. This is because fat-soluble toxins are stored in the fat reserves of animals, and then bioaccumulate up the food chain. So in this case, most of the toxin is not secreted, but stored within the food chain, and bioaccumulates, with the concentration becoming higher the further up the food chain.
Due to a genetic modification, a mouse has no horizontal cells in its retinas and it does not expresses the connexin26.
What is horizontal cells?
The horizontal cells has receptive field with the neurobiotin and controlled by the electrical coupling.
Horizontal cells are the laterally interconnecting neurons having cell our bodies withinside the internal nuclear layer of the retina of vertebrate eyes. They assist combine and alter the enter from a couple of photoreceptor cells.
To read more about the horizontal cells refer link :
brainly.com/question/25508290
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