Insight-HXMT spectrum from 2018 April 8 (ObsID P011466101502). Top panel: Spectrum fit with the model TBabs × constant × TBabs × (diskbb + gaussian + relxill). The black datapoints show observation intervals in which QPOs are detected, and red datapoints show non-QPO intervals. Middle panel: Residuals for the same spectral model. Bottom panel: Residuals when the same spectrum is fit with the simpler model constant × TBabs × (diskbb + gaussian + cutoffpl), i.e., without disk reflection.