A Reflection Nebula Is Made Visible by

A reflection nebula is made visible by

A) thermal energy emitted as a continuous spectrum by the very hot gas, much like that emitted by a hot body on Earth.
B) light from embedded stars reflected over a wide range of wavelengths toward Earth by crystals of water, methane, and ammonia ices.
C) emission lines from hydrogen, which itself has been ionized by UV light from embedded stars.
D) blue light preferentially scattered by dust grains.