We See an Emission Nebula Predominantly In

We see an emission nebula predominantly in:

A) blue light, originally emitted by stars within the nebula but scattered by dust.
B) light emitted over a wide range of wavelengths by dust grains that have been heated by radiation from embedded stars.
C) light emitted by molecules in the dense clouds of gas surrounding the stars in the nebula.
D) the Balmer H_α red line, from recombination of electrons with nuclei in ionized hydrogen.