The correct answer is (b). Carbon is the most necessary fundamental element in all bio-compounds. It is the main component of organic compounds, which are the building blocks of living things. Carbon atoms can bond with each other in a variety of ways, which allows them to form a wide range of compounds. Carbon is also able to bond with other elements, such as hydrogen, oxygen, nitrogen, and sulfur, which further increases the diversity of organic compounds.
Sulphur is an essential element for some organisms, but it is not as common as carbon. Oxygen is also an essential element, but it is not as important for the structure of organic compounds as carbon. Nitrogen is an important element for some organisms, but it is not as common as carbon or oxygen.
In conclusion, carbon is the most necessary fundamental element in all bio-compounds. It is the main component of organic compounds, which are the building blocks of living things. Carbon atoms can bond with each other in a variety of ways, which allows them to form a wide range of compounds. Carbon is also able to bond with other elements, such as hydrogen, oxygen, nitrogen, and sulfur, which further increases the diversity of organic compounds.