Which of the following are diastereomers?

The Fischer projection of (I) and (II) is wrong because the functional group is not at the top. on rotating (I) and (II) by 180°, they are represented as shown:Now compare I, II, III, and IV.(I) and (III) ⇒ Enantiomers(II) and (IV) ⇒Identical or sameTherefore, the pairs of diastereomers are:(I), (II) (D, (IV); and (II), (III).But the answer given is (3) (I, II).