Answer:
When you exercise, the muscles you use require more energy. When exercise can be sustained, this demand is met primarily by aerobic means. Aerobic energy production in muscles results in increased gas exchange at the lungs, because more oxygen is taken in and more carbon dioxide is released.
Explanation:
A cave, from the water slowly cracking and chipping away at the rock it seeps down into, creating freshwater, but also, slowly creating a cave.
