Final answer:
It is false that rainbows can occur without sunlight; they require sunlight to be refracted and reflected within raindrops, dispersing the light into a spectrum of colors visible as a rainbow.
Step-by-step explanation:
It is false that rainbows can occur without sunlight. Rainbows are produced by a combination of refraction and reflection of sunlight. When sunlight encounters raindrops, it enters the drop and is refracted (or bent) and reflected. As light exits the raindrop, it is refracted once again, and because the index of refraction of water varies with wavelength, the light is dispersed into the spectrum of colors that we see as a rainbow. This effect is most remarkable when the background is dark, such as during stormy weather, but can also be seen around waterfalls and lawn sprinklers. You must be between the Sun and a rain shower with the Sun behind you to witness a rainbow.