Emission and reflection nebulae differ primarily in their interactions with light. Emission nebulae glow brightly due to the ionization of their gas by the ultraviolet radiation from nearby hot stars, causing them to emit light at specific wavelengths. In contrast, reflection nebulae do not emit their own light; instead, they scatter and reflect the light from nearby stars, which causes them to appear bluish. Therefore, the correct response is:
interactions with light.