How might a change of one amino acid at a site, distant from the active site of an enzyme, alter the substrate specificity of an enzyme? by changing the optimum ph for the enzyme by changing the stability of the enzyme by changing the binding site for a noncompetitive inhibitor by changing the three-dimensional conformation of the enzyme?

The correct answer is: by changing the three-dimensional conformation of the enzyme.
 Enzymes like all the other proteins are shaped by interactions between their amino acids and when those interactions change, the 3D structure of the enzyme changes (tertiary structure). A change in shape will change the shape of the active site and the substrate cannot bind.