Why Do We Find Methane Clouds Above Water Clouds in the Atmosphere

Why do we find methane clouds above water clouds in the atmosphere of Saturn?

A) Methane clouds are less dense than water clouds.
B) Methane is far more plentiful than water on Saturn.
C) Methane is in a gas state at lower temperatures than water.
D) We can't observe the methane clouds that are deeper in the atmosphere.
E) all of these