Imagine that it is the first really cold night of the winter season. You begin to feel a chill in the house so you decide it's time to turn on the furnace. So you get up out of your chair and adjust the thermometer. After a while you notice that it has not really warmed up much in the house. So you decide to check it again just as soon as you get something for this awful headache that just came on. But, as you get up out of your chair you almost fall over because you are so dizzy. You also begin to feel weak and nauseous. You think that ....