Question

which of the following are luminous?
candle flame, humans
campfire, star, sun
paper, rainbows, stars

Explanation:

Luminous objects emit their own light. A candle flame emits light due to combustion, but humans do not (they reflect light). Campfire emits light from burning fuel, stars (including the Sun) emit light from nuclear fusion. Paper reflects light, rainbows are a reflection and refraction of light (not emitting their own), and while stars are luminous, the combination in the third option is incorrect as paper and rainbows are not.

Answer:

campfire, star, Sun