Which of the Following Best Describes the Nature and Origin

Which of the following best describes the nature and origin of the atmospheres of the Moon and Mercury?

A) They have thin tropospheres only,with gas coming from evaporation and sublimation.
B) They have thin exospheres only,with gas coming from impacts of subatomic particles and photons.
C) They have only small amounts of gas,all of which is leftover from outgassing long ago.
D) They have very thin atmospheres produced by outgassing,but still have the layers of a troposphere,thermosphere,and exosphere.