Calcium is one of the most abundant elements in all living things. Thus, the correct option is D.
The essential elements found in living entities are carbon, oxygen, hydrogen, and nitrogen. Carbon is present at almost 20% in the mass. It is the building unit of the living compounds.
Calcium is the most abundant element in all living things because it is the source of a component that forms bones in living compounds. Bones are present in large numbers in animals including humans.
Therefore, the correct option for this question is D.
To learn more about the Components of living organisms, refer to the link:
https://brainly.com/question/17259533
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