Climate, I think.
Costa Rica has billboards all over Canada (where I live) that advertise Costa Rica. Come to think of it, I haven't seen one of those in a while, but I'm sure I did. Our winters are horrible, cold and (this year) very long.
I think A. The acid dries up the water, is the answer
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon Dioxide almost 0.1%
