Two example composite spectra observed by LAMOST. Top panel: main-sequence M giant binary. The molecular bands suggest a classical M giant spectrum in the red part, while the Balmer absorption lines suggest an F-type main-sequence spectrum in the blue part. In our M giants catalog, early-type binaries were labeled non-M giants. Bottom panel: white dwarf–M dwarf binary, which show pressure-broadened Balmer series in the blue part and strong molecular lines in the red part. Note that these stars are labeled white dwarf binaries in the M giants catalog.