Which sentence from the article shows Alaska's MAIN problem?

A
Anchorage, Alaska, experienced record warmth and set a snowfall record on the same day.
B
Anchorage is a city that picked up a record 8.4 inches of snow and set a record warm high temperature on November 16.
C
On November 16, a brief southerly wind ticked the thermometer from freezing to the mid-40s in two hours shortly after midnight.
D
Much of Alaska's recent warmth can be traced to disappearing Arctic sea ice in the Chukchi and Bering Seas.