Mass Spectrometry

Step 1: Mass Spectrum of 2-Pentanone.
In the mass spectrum of 2-pentanone, the molecular ion (M+) peak is at m/z = 86. This corresponds to the molecular weight of 2-pentanone. The main fragmentation pattern occurs due to the loss of groups like CH3 (m/z = 15), CH2CH3 (m/z = 29), and smaller ions like m/z = 57.

Step 2: Conclusion.
Thus, the correct set of peaks is m/z = 86, 57, 29, which corresponds to option (2).

Final Answer: