Question

What is the percentage of Oxygen in the Earth’s atmosphere?

A. 42.94%

B. 20.95%

C. 35.94%

D. 25.94%

Answer 1

Hint: The atmosphere is composed of a mix of several different gases in differing amounts. The permanent gases whose percentages do not change from day to day in decreasing order are nitrogen, oxygen and argon. 

Complete answer:

Let us analyse the atmosphere and its composition to begin with before eventually arriving at the answer to this question.

Earth is the only planet in the solar system with an atmosphere that can sustain life. The blanket of gases not only contains the air that we breathe but also protects us from the blasts of heat and radiation emanating from the sun. It warms the planet by day and cools it at night.

Earth's atmosphere is about 300 miles (480 kilometres) thick, but most of it is within 10 miles (16 km) of the surface.

Air pressure decreases with altitude. At sea level, air pressure is about 14.7 pounds per square inch (1 kilogram per square centimetre). At 10,000 feet (3 km), the air pressure is 10 pounds per square inch (0.7 kg per square cm). There is also less oxygen to breathe.

According to NASA, the gases in Earth's atmosphere include:

-Nitrogen — 78 percent

-Oxygen — 21 percent

-Argon — 0.93 percent

-Carbon dioxide — 0.04 percent

-Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor.

Thus, the answer to this question per our analysis is (B).

Note: Oxygen plays a critical role in respiration, the energy-producing chemistry that drives the metabolisms of most living things. We humans, along with many other creatures, need oxygen in the air we breathe to stay alive.