For the equation to balance out, you would need 2 H2O on the product. That will give a total of 1 Carbon, 4 Hydrogens and 4 Oxygens on each side.
O.N. of Na = +1
O.N. of O = -2
Let, O.N. of Tin = x
1*2 + x + -2*2 = 0
2+x-4 = 0
x-2 = 0
x = 2
SO OPTION C IS YOUR ANSWER......
The generic solution of the reaction that occurs would be writen as water + anhydrous salt = hydrated salt
chemical equation would look like this xH2O +AB = AB.xH2O
