Gloria drove from sea level to the top of a tall mountain. As she strolled around the top of the mountain,...

1. Gloria drove from sea level to the top of a tall mountain. As she strolled around the top of the mountain, she noticed that she was breathing faster and deeper than usual. Why was this change in Gloria's breathing useful? (Hint: Air pressure is significantly lower at high altitudes than at sea level, so there is less O2 in a given volume of air.)
During vigorous exercise your breathing will become faster and deeper. Exercise is a _________.