Diffusion is the movement of a solute from an area of its high concentration to an area of its low concentration – i.e. down a concentration gradient. This process is “passive” – i.e. it requires no energy; the gradient is enough to drive the process.
CH4 + 2O2 --> CO2 + 2H2O
On the reactant side you start with 1 carbon, 4 hydrogen, and 2 oxygen. On the product side you start with 1 carbon, 2 hydrogen, and 3 oxygen. In order to get them equal, you need to put 2 in front of the H2O which equals out the number of Hydrogen on both sides. But Now we must balance the Oxygens. Because of the H2O we now have 4 Oxygens on the product side and only 2 on the reactant. In order to balance this, we put a 2 in front of the O2 giving us 4 hydrogen on both sides, Balancing the equation
The answer is A but i'm not sure .