Question

The four elements that make up 99% of all elements found in living system are
A. C, H, O and P
B. C, H, O and S
C. C, H, O and N
D. C, N, O and P

Answer 1

Hint: Living system is made up of matter at a fundamental level. The matter is defined as any substance that occupies space and has mass. The simplest form of matter is called elements. There are a total of 118 elements which are also mentioned in the form of the periodic table. Among these only 92 elements occur naturally.

Complete answer: Carbon, hydrogen and oxygen is the most abundant element present in the human body with 18.5%, 9.5% and 65% respectively in the form of carbon dioxide and water or intake of these elements in the form of carbohydrates. As shown in the table above P i.e. Phosphorus is present in less percentage.
Option B- C, H, O, and S: As shown in the table above S i.e. Sulphur is present in less percentage. Sulfur is found in the form of amino acids, proteins, enzymes, vitamins, etc.
Option C- C, H, O, and N: As shown in the table above N i.e. Nitrogen is present in 3.2%. Nitrogen is found in the form of proteins in hair, skin, muscle and other tissues forming the building blocks of the body.
Option D- C, N, O and P: Phosphorus is mainly found in the teeth and bones and is interrelated to calcium in regulating hormones and metabolism of minerals.
Thus, the correct option is option C- C, H, O, and N i.e., Carbon, hydrogen, oxygen, and nitrogen.

Note: Oxygen is not only abundant in the human body but also the atmosphere and earth’s crust with 21% and 46% respectively while nitrogen is the most abundant element found in the atmosphere with 78%. Others are present in traces. All the elements obey both chemical and physical law in living and non-living systems.