(B) Refraction, dispersion and internal reflection
Water droplets refract and disperse sunlight, then internally reflect it, and refract it again on exit, forming the rainbow.
Source: Chapter 10, Section 10.4 Dispersion of White Light by a Glass Prism
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The textbook explicitly states: "They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop." The key word is internal reflection (not total internal reflection — option D also wrongly adds scattering). Option (A) says plain "reflection" which is incorrect. The correct phenomena are refraction + dispersion + internal reflection → Option (B).