While en route at 7,500 feet MSL in an unpressurized airplane without supplemental oxygen, you become anxious after a difficult position report exchange with ATC and begin breathing rapidly. You then notice tingling in your fingers and toes, lightheadedness, and blurred peripheral vision. What is the MOST LIKELY cause of these symptoms, and what is the PRIMARY corrective action?

While climbing from an airport at sea level, you experience severe pain in your ears due to a head cold. What is the BEST immediate corrective action?

You are on a daytime VFR cross-country flight at 12,500 feet MSL in an unpressurized light airplane without supplemental oxygen. You begin to experience a throbbing headache, slowed reaction time, and a feeling of well-being despite deteriorating flight performance. What is the most appropriate immediate corrective action?

Prior to takeoff on a VFR cross-country flight, you have a head cold with significant sinus congestion. What is the best course of action?