Which of the following can be achieved by using a visible-light spectrophotometer?
I. Detecting the presence of isolated double bonds.
II. Finding the concentration of a KMnO₄ solution.
III. Running a flame test to determine if Na+ or K+ is in a solution.
(A ) III only
(B ) II only
(C) I only
(D) II and III
(E ) I and II