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?

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?

While using the cabin heater during flight on a cold day, you detect a faint exhaust odor followed shortly by a dull headache and drowsiness. The MOST APPROPRIATE immediate action is to

During cruise flight at 4,000 feet AGL, you increase the cabin heat setting. About 10 minutes later, you develop a headache, dizziness, and mild nausea. What is the MOST APPROPRIATE immediate action?