Answer:
The answer is C.2,1,2
Step-by-step explanation:
The reason why the answer is C.2,1,2 is because if you put a 2 Infront of the first calcium it will be balanced with the calcium in the product side and if you put one in front of the oxygen that wiil be two and it will also be balanced with the oxygen on the product side and seeing that a 2 the coefficient is already on the product side the equation is already balanced