The answer to the question is : B: 6;6
There are __6__ different types of air masses that coming from _6___ different locations that influence the weather in North America., namely :
a) Continental Polar ; Large sub polar land area b) Continental Arctic ; Canada, United States c) Continental Antarctic ; Antartica d) Continental Tropical ; Sahara, Arabian & Australian Deserts e) Maritime Polar ; Polar Oceans f) Maritime Tropical ; Rocky Mountains