What is the ratio of moles of MgO to moles Fe?

Answer:
3:2, B
Explanation:
The mole ratio is simply the coefficients in a balanced chemical reaction and their relation to each other.
One simple way to easily know b is the correct answer is to look at the units for the answer choices. A is a ratio of Fe to Fe, C is a ratio of Mg to Fe, and d is a ratio of Mg to Fe. That alone must mean B is the correct answer.
We can also use the definition of a mole ratio, as stated above. Given that this equation is balanced, the mole ratio is simply the ratio of the coefficients, and is thus 3:2.