The answer here is 9. PH value is a logarithmic scale, with 0 representing a neutral value, 1 representing an acidic solution, and any value greater than 1 representing a basic solution. Since MgS203 has a PH value of 4.0, we know that its PH value is higher than the neutral value of 7, making it a basic solution. Choice D is the only value greater than 1, making it the correct answer. Thus, the PH value of a basic solution is anything greater than 7.