How is the existence of Earth's unique atmosphere explained?
A)The oxygen in Earth's atmosphere is a result of early life on Earth.
B)Volcanic gases containing nitrogen were outgassed from Earth's interior.
C)As Earth cooled, water vapor fell out of the atmosphere to form the oceans.
D)Ultraviolet radiation from the Sun freed the hydrogen, allowing it to escape.
E)When Earth formed, its atmosphere formed from the gases most common in the early solarsystem.

Question

Quizplus · Accepted Answer

The presence of oxygen in Earth's atmosphere is largely due to the photosynthetic activity of early life forms on the planet.

How Is the Existence of Earth's Unique Atmosphere Explained