Why Do We Think That Venus Has So Much More

Why do we think that Venus has so much more atmospheric gas than Earth?

A) Venus has gained much more gas through outgassing than has Earth.
B) Because of its lack of magnetic field,Venus has been able to gain gas through the impacts of solar wind particles,while Earth has not gained gas in this way.
C) Earth has lost much more gas to thermal escape than has Venus.
D) Most of the gases that have been released from volcanoes on Earth later returned to the surface.