I think it would be A. Because plants have bacteria on their roots that take the free nitrogen in the air from the soil and turn it into usable nitrogen. Animals could get usable nitrogen from eating plants since they have bacteria that make it. Then if an animal eats an animal that ate the plant, then it could get that nitrogen. But i am not completely sure though. I just learned this recently. I hope this helped :)
Answer:
A= The size of an atom is smaller than the size of a sand particle on a beach.
The size is basically really really small, and you cannot see it in the naked human eye.
Answer:
A
Explanation:
I just learned about it myself.
