How Is the Existence of Earth's Unique Atmosphere Explained

Multiple Choice

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.