Final answer:
The correct coefficients that balance the equation are 2, 1, 2.
Step-by-step explanation:
To balance the formula equation CaO + H₂O → Ca(OH)₂, we need to adjust the coefficients. The correct coefficients are a. 2, 1, 2. This means that the balanced equation is 2CaO + H₂O → Ca(OH)₂.