The elemental composition of an adult human body by mass is

[amp_mcq option1=”C > O > H > N” option2=”O > C > H > N” option3=”N > C > H > O” option4=”N > C > O > H” correct=”option2″]

This question was previously asked in

UPSC CDS-2 – 2016

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The elemental composition of an adult human body by mass is dominated by Oxygen, followed by Carbon, Hydrogen, and Nitrogen.

Oxygen is the most abundant element by mass (approx. 65%), largely due to its presence in water (H₂O). Carbon (approx. 18.5%) forms the backbone of organic molecules. Hydrogen (approx. 9.5%) is also abundant in water and organic compounds. Nitrogen (approx. 3.2%) is a key component of proteins and nucleic acids.

These four elements constitute about 96-97% of the human body’s mass. Calcium and Phosphorus are the next most abundant elements, primarily found in bones and teeth.

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