  The magneto-optical spectra of ABC-stacked trilayer graphene are enriched by
the electric field. A lot of prominent absorption peaks, which arise from the
inter- Lnadau-level transitions, gradually change from the twin-peak structures
into the double-peak ones with the increasing electric-field strength. This
comes from the de- struction in mirror symmetry of xy-plane and the
non-equivalence for two sublattices with the identical projections. Specially,
a single threshold peak becomes a double- peak structure, owing to the
Fermi-Dirac distribution. The absorption frequencies continuously grow or
decline except for the anti-crossings of Landau levels. Also, such
anti-crossings can induce extra double-peak structures.
