4. Which of the following statements regarding EDTA titration are correct?
(1) Back-titration should be used if analyte does not have satisfactory indicator.
(2) If the pH is lowered, the conditional formation constant decreases, and the end pointbecomes more distinct.
 (3) The pH cannot be raised arbitrarily high, because metal hydroxide might precipitate.
 (4) Anions that precipitate with certain metal ions can be analyzed with EDTA bydisplacement titration method.
(5) Trivalent cations can usually be titrated without interference from divalent species bymaintaining the solution even at a pH = 1.
 Your answer:
(A) (1) and (5)；
(B) (1), (3) and (5)；
(C) (1), (3) and (4)；
(D) (2), (4) and (5)；
(E) (1), (2) and (3).