Explanation:

- Bleaching powder is commonly used for disinfection and bleaching purposes due to its chemical properties.

- Option 1: Nitrogen - Not a component of bleaching powder.

- Option 2: Iodine - Not found in bleaching powder.

- Option 3: Chlorine - Correct. Bleaching powder contains chlorine in the form of calcium hypochlorite, which gives it strong oxidizing and bleaching properties.

- Option 4: Bromine - Not present in bleaching powder.