Which is the most important component of air for human existence?

Correct option is D

• Oxygen is the most important component of air for human existence. Humans require oxygen for cellular respiration, a process in which oxygen is used to break down glucose to release energy for the functioning of the body. Without oxygen, human life would not be sustainable, as the body depends on it for survival and metabolism. The concentration of oxygen in the air is about 21%, and it is crucial for the survival of most living organisms on Earth.

• Oxygen is essential for cellular respiration, where glucose is broken down to produce energy in the form of ATP.
• The human respiratory system is designed to take in oxygen from the air and transport it to the bloodstream, where it is then distributed to tissues and organs.
• A lack of oxygen in the air, as seen in high-altitude environments or poorly ventilated spaces, can lead to hypoxia, which can cause serious health problems or even death.
• Oxygen is used by all aerobic organisms (including humans) to sustain life and support vital biological processes.
• While the Earth's atmosphere is composed primarily of nitrogen (78%), it is the presence of oxygen that makes life as we know it possible.
• Oxygen also plays a critical role in combustion and the breakdown of organic matter in ecosystems.

• Nitrogen: Nitrogen makes up about 78% of the atmosphere and is inert, meaning it does not directly support human life. However, it is essential for the nitrogen cycle, which helps in the formation of proteins and other compounds.
• Carbon: Carbon is a critical element for life, especially in the form of carbon dioxide (CO₂), which plants use in photosynthesis. However, excess CO₂ in the atmosphere leads to climate change, and it is not directly used for human survival like oxygen.
• Helium: Helium is a very light, inert gas present in small quantities in the air. It does not support life and is primarily used in applications such as balloons, cooling systems, and medical devices.