Question

What is most important for life :
A)Carbon
B)Oxygen
C)Water
D)Nitrogen

Answer 1

Life is a characteristic feature that distinguishes living organisms from non-living. Life exists in various forms such as plants, animals, protists, fungi, archaea, and bacteria. Some characteristics of life are- response to the environment, growth and change, ability to reproduce, have a metabolism, maintain homeostasis, cellular mechanism, etc.

Complete answer:
Option A- Carbon
Carbon is the main element in compounds that are especially found in living things, i.e., Organic compounds. Carbon is present in the atmosphere in the form of $CO_{2}$ , $CH_{4}$ (methane).

Option B- Oxygen
Oxygen plays an important role in almost all of the living reactions like photosynthesis, respiration, energy production, etc. Oxygen is present in the atmosphere in about 21%. It is the third most abundant element in the atmosphere. It helps in providing oxidized media and does not allow a reducing atmosphere.

Option C- Water
Water is necessary for carrying nutrients to all the cells of the body and oxygen to the brain. Water is responsible for absorbing minerals, vitamins, amino acids, etc. About 60% of our body is made up of water.

Option D- Nitrogen
Nitrogen is important for the synthesis of amino acids, nucleic acids, proteins, etc. Nitrogen is the most abundant element in the atmosphere, i.e., 78%. It is essential for life because it is an important building block of DNA.

Hence the correct answer is OPTION(B)

Note: The term Oxygen was coined by Antoine Lavoisier in 1777. Oxygen is present in the atmosphere in the form of the oxygen molecule, i.e., $O_2$. It is present especially in the troposphere. Oxygen present in the stratosphere is in the form of Ozone, i.e., $O_3$. Ozone prevents the entry of harmful UV rays from the sun.