How is cold front formation different from stationary front formation?

a - Stationary fronts form between warm and cold air masses, while cold fronts form when a cold air mass advances against a warm air mass.
b - Cold fronts form between two air masses that barely move, while stationary fronts form when a warm air mass is trapped between two cold air masses.
c - Cold fronts form when a warm air mass moves over a cold air mass, while stationary air fronts form when a cold air mass moves over a warm air mass.
d - Stationary fronts form when a warm air mass is trapped between two cold air masses, while cold fronts form when a warm air mass moves over a cold air mass.