On Mars, the Air Pressure Varies Much More from One

On Mars, the air pressure varies much more from one season to another than it does on Earth. Why is this?

A) Seasonal dust storms on Mars blanket the entire planet, increasing the weight of the atmosphere.
B) Because the atmosphere of Mars is so thin, water vapor condensing on the polar ice caps in winter removes a much larger fraction of the atmosphere than on Earth.
C) Because of the low density of the atmosphere, solar heating has a much larger effect on Mars than on Earth.
D) On Mars, much of the CO₂, the major constituent of the atmosphere, condenses out to the surface as snow. This gas is only a minor constituent in Earth's atmosphere.