I am pretty sure the answer is B but correct me if I'm wrong hope this helps.
It is mostly used in applications that need measuring substances that would have a<span> relatively neutral pH . </span>A<span> common use is for measuring the presence of carbonic </span>acid<span> in </span>a<span> liquid. so yes its acidic</span>
I believe it would be 7.731. x 10^5? That is if they want you to evaluate.