The correct answer for this is B. Count up the atoms. They should be equal for each side of the equation.
Answer:
B. 2HgO → 2Hg + O2
Explanation:
In order to have a correctly balanced equation, you need to have the same amount of elements and molecules of those given elements in both sides of the equation, so in this one there hare 2 molecules of Hg and 2 of Oxygen in the left, and in the rigth, there are 2 Hg, and one molecule of O2 which are 2 molecules of oxygen. So the one that is correctly balanced is B. 2HgO → 2Hg + O2