In the cases of warm and cold fronts, the warm air rises above the cold air because: warm air is dense than cold air b. thunderstorms force warm air...

In the cases of warm and cold fronts, the warm air rises above the cold air because:

a. warm air is dense than cold air 

b. thunderstorms force warm air upward in their updrafts 

c. cold air is affected by gravity and warm air is not 

d. all air moves upward in anticyclones