Physics · GRAVITATION

The Moon has no atmosphere because:

1. A
   The root mean square speed of gas molecules can exceed the escape velocity from the Moon's surface.
2. B
   The Moon revolves around the Earth synchronously in 27.3 days.
3. C
   The acceleration due to gravity on the Moon is larger than that on Earth.
4. D
   The gravitational force on the Moon acts towards the Earth instead of the Moon's center.