The three 'H NMR spectra below are for three different structural isomers (out of a possible four) of alcohols having a molecular formula C4H10O (inset: appearance of the indicated section of the spectrum after addition of D2O). Draw the structural formulae of the four different isomers. Then interpret the NMR spectra as fully as possible in order to identify the three isomers concerned:
After addition of D2O