Are there more than one air mass if so. plz

Yes because as you go up in the atmosphere the air get thinner

Yes . an air mass is a block of air that causes change in weather in other countries . There are 5 main air masses . These are called Tropical Maritime ( which is associated with hot and wet weather and comes from Portugal ) , Tropical continental  ( hot and dry from Africa ) , Polar Maritime ( cold and wet from the Atlantic  ocean ) , Polar Continental ( cold and dry from Russia ) and Arctic Maritime ( Cold and dry from the Arctic ocean ) .

The answer would be d. pili