The colors seen in a rainbow

Question

$\begin{array}{1 1} \text{a.are produced by raindrops of different colors.} \\ \text{ b.are produced by raindrops of different shapes.} \\ \text{ c.are produced when sunlight is refracted by raindrops.} \\ \text{ d. are the colors of the different atoms that make up water.} \end{array}$