An unknown compound shows a weak molecular ion at m/z 87 in the mass spectrum, and the only large peak is at m/z 30. The IR spectrum appears below. The NMR spectrum shows only three singlets: one of area 9 at 0.9 ppm, one of area 2 at 1.0 ppm, and one of area 2 at 2.4 ppm. The singlet at 1.0 ppm disappears on shaking with D2O. Determine the structure of the unknown compound.