What Is the Cause of Canada's Arctic Deserts Like Those

Multiple Choice

What is the cause of Canada's Arctic deserts like those on Cornwallis and Ellismere Islands?

A) permanent high pressure and dry north polar easterlies
B) a rainshadow from the Mackenzie Mountains in the Northwest Territories
C) overgrazing by musk oxen and melting of the Arctic ice cap
D) subtropical high from the descending limb of the Tropic of Cancer's Hadley cell