Compounds C and D are isomers with the formula C9H12, in addition to other absorption peaks, both compounds show a peak near 7.25 ? (area 5) in their 1H-NMR spectra. Their mass spectra are as follow, show the structures of C and D.

100 105 Mass spectrum of C 50 120 77 31 39 91 20 30 40 50 70 60 120 80 90 100 110 130 140 100 91 Mass spectrum of D 50 120 65 39 78 51 105 0. 20 30 40 50 60 70 80 90 100 110 120 130 140 Relative abundance Relative abundance