The electromagnetic radiation used to kill germs in water purifiers is

Ultraviolet rays

The correct answer is Option (4) → Ultraviolet rays

Ultraviolet (UV) rays have high energy and short wavelength. When water is exposed to UV rays, the radiation penetrates microbial cells and damages their DNA or RNA, preventing them from reproducing and effectively killing or inactivating bacteria, viruses, and other pathogens. This property makes UV rays suitable for sterilization in water purifiers.

Correct answer: Ultraviolet rays