Answer to Question 1
The major component of Mars' atmosphere, carbon dioxide, freezes out as dry ice every winter, forming a huge but very thin polar cap. But in the opposite hemisphere, that cap is subliming back into the atmosphere, creating a high pressure area above it. With the changing seasons, the atmosphere flip-flops from pole to pole, with great barometric pressure changes and hurricane force winds and dust storms observable from Earth.
Answer to Question 2
B