28. For Infrared spectra, which statement below is correct ? (A) trans-Mo(CO)2(PMe3)4 has one CO IR active stretching signal (B) symmetric stretching of cis-Mo(CO)2(PMe3)4 is IR inactive (C)CO ligand has higher frequency than CN- ligand (D) Terminal CO ligand usually has lower frequency than bent NO (E) fac- and mer-Mo(CO)3(PMe3)3 cannot be distinguished by IR