Available options: (I) sunlight (II) streams (III) photons (IV) water vapor (V) water cycles (VI) water tables (VII) just light (VIII) condensation

Fact 1: Arainbow is formed by refraction of light by separating light into all different colors. Fact 2: Water vapor bends the light. Given the two facts above, rainbows are formed via ?
Answer:
(IV)