The answer is visible rays. For example, when a rain storm stops, the sun comes out and you are likely to see a rainbow. This is because the sun shines on water molecules in the air and the colors appear. These colors are called visible light. The only ray that a naked Human eye can see
12 sub levels are in an atom
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.