Answer:
The answer is a. CH4 + 2O2 --- CO2 + 2H2O
Step-by-step explanation:
A balanced chemical reaction must have the same number of each type of atom on both sides according to the law of conservation of mass:
1 carbon 4 hydrogen + 4 oxygen ----- 1 carbon 2 oxygen + 4 hydrogen
2 oxygen =
1 carbon 4 hydrogen 4 oxygen ---- 1 carbon 4 hydrogen 4 oxygen
Since each type of atom has the same amount on both sides, the chemical formula is balanced.