A few other ways to help:
Class B - B is for "blue," the blue circles outlining the Class B airspace. Think of it as if you're a little kid; you have to ask permission before doing ANYTHING involving Class B airspace.
Class C - C is for "call," since it's like Class B but not quite as strict. Two-way radio communication required with ATC prior to entering Class C airspace, but not an official clearance like with Class B.
"In this present crisis, government is not the solution to our problem - government IS the problem." - Ronald Reagan
Comments made here are my own and are not intended to represent the official position of Alaska Air Group