Sun's halo is produced by the refraction of light in

1. A Sun's halo is an optical phenomenon that appears as a ring of light around the Sun. 2. Halos are formed by the refraction (bending) and reflection of sunlight by millions of tiny hexagonal ice crystals suspended in the atmosphere. 3. These ice crystals are typically found in high-altitude clouds, specifically Cirrus or Cirrostratus clouds (Option C). 4. Cirrocumulus clouds (Option B) also contain ice crystals but usually produce coronas (smaller colored rings closer to the Sun) rather than halos. 5. Stratus clouds (Options A and D) are low-altitude clouds composed primarily of water droplets, not ice crystals, and do not typically produce halos. Water vapour itself (Option A) or dust particles (Option D) do not cause halos.