Spectrum C:
The splitting and the integration of the three multiplets strongly suggest an n-propyl group attached to a strongly electronegative group such as O (too downfield for Br, and anyway 1-bromopropane wouldn’t have enough for the formula). We have only one DBE, and the 13C NMR strongly suggests that we have an ester present. We have a CH2Br left over, giving the structure shown. Note that if the CH2Br were directly attached to the O of the ester, it would be at around 5 ppm, and the end CH2 of the propyl would be only at around 2.3 ppm, so we can rule out the isomer, bromomethyl butanoate.