The correct answers are:
- Polar air mass;
- Continental air mass;
The polar air masses form predominantly over land, or rather ice. They form over the poles and their close proximity, with the ones forming on the south pole being formed directly over Antarctica as a land mass, while the ones on the north pole being formed over ice, or rather the frozen ocean. They are very cold and very dry air masses.
The continental air masses form above land, deeper into the mainlands of the continents, which is why that have this name. They can be either very cold and dry in winter, or very hot and dry in the summer.