I'm not positive, but I believe it would be one near the Rocky Mountains.
They convert chemical potential energy (stored in muscle cells) to kinetic energy (running)
As the volume of a gas increases <em>at constant temperature</em>, the number of particle impacts per unit area decreases.
There is the same number of impacts, but they are spread over a larger surface area.
Thus, the number of impacts per unit area decreases.
To calculate atomic mass, you have to take to weighted average of the isotopes' masses. What that means is M = RA*106 + (1 – RA)*104, where RA is relative abundance expressed in decimal form. If you simplify the right side of that equation, you get M = 2*RA + 104. Doing a little more algebra yields RA = (M –104)/2 = (104.4 – 104)/2 = 0.4 / 2 = 0.2, which is 20%. So the answer is B.