Deduce the identity of the following compound from the ¹³C NMR data given.
C₉H₁₂: δ 21.3 (quartet), 127.2 (doublet), 138.0 (singlet) (ppm)

Quartet

In NMR spectroscopy, a signal pattern of four peaks indicating the splitting of a signal due to coupling with three equivalent protons.

Doublet

In spectroscopy, a pair of closely spaced energy levels or lines, often observed in the spectra of atoms and molecules.