Concept:A natural source of light produces its own light and is not made by people.Explanation:A glow worm makes its own light by a chemical reaction in its body (bioluminescence), so it is a natural source.Lanterns and torchlights are man-made (artificial) sources. The moon is not a source at all: it only reflects sunlight.Key point: The moon is a non-luminous body; it shines only by reflected light from the sun.Answer:Option C (glow worm)