The characteristic property of the solution is:

a) Formation of the solution is a physical change

b) Solute and solvent in the solution can be separated by filtration

c) Solute and solvent in the solution can be separated by decantation

d) Solution can be represented with a chemical formula

We know that there is no chemical reaction between solute and solvent. Hence the solution is a physical change. (a) is correct.

And, by using filtration and decantation we will not be able to separate the components of the solution. Hence, (b) and (c) is incorrect.

We also know that solution is a homogeneous mixture, and it cannot have any particular chemical formula. Hence, (d) is also incorrect.

Hence, option B is the answer.