COTD: It Isn't 50

Bastardi: Just Say No to El Nino, at least till 2012 | Watts Up With That?: "rbateman says:
July 22, 2011 at 10:51 pm
Here’s one for the Climate Change pop quiz:
I have a box. It’s filled with normal air. The box is just big enough that it contains 1 co2 molecule, at the present rate of 390 ppm co2. How many other molecules are in the box?
a.) 100
b.) 50
c.) 2,564
d.) 390"