To balance a chemical equation we need to make sure that the number of atoms of each element before and after the reaction occurs is the same.
In this case, we're asked to balance the equation:
As you can see, to balance Hydrogen we could multiply the coefficient of the products where Hydrogen is, by 2. Then, counting again:
Finally, we need to balance oxygen. For this, we could multiply the coefficient of O2 by 2 so we can have the same number of Oxygen atoms before and after the reaction occurs. Therefore, the balanced reaction is:
And, the coefficients when the equation is balanced, are:
__1_ CH4 + _2__ O2 = __1_ CO2 + __2_ H2O.
So, the correct answer is 1,2,1,2.