  We present the study on GRB 071112C X-ray and optical light curves. In these
two wavelength ranges, we have found different temporal properties. The R-band
light curve showed an initial rise followed by a single power-law decay, while
the X-ray light curve was described by a single power-law decay plus a
flare-like feature. Our analysis shows that the observed temporal evolution
cannot be described by the external shock model in which the X-ray and optical
emission are produced by the same emission mechanism. No significant color
changes in multi-band light curves and a reasonable value of the initial
Lorentz factor ({\Gamma}0 = 275 \pm 20) in a uniform ISM support the afterglow
onset scenario as the correct interpretation for the early R-band rise. The
result suggests the optical flux is dominated by afterglow. Our further
investigations show that the X-ray flux could be created by an additional
feature related to energy injection and X-ray afterglow. Different theoretical
interpretations indicate the additional feature in X-ray can be explained by
either late internal dissipation or local inverse-Compton scattering in the
external shock.
