Exposure to sunlight helps a person improve his health because

resistance power increases
the infrared light kills bacteria in the body
the ultraviolet rays convert skin oil into Vitamin D
the pigment cells in the skin get stimulated and produce a healthy tan

The correct answer is: C. the ultraviolet rays convert skin oil into Vitamin D.

Vitamin D is a nutrient that the body needs for many important functions, including building and maintaining strong bones. It is also important for the immune system, nervous system, and muscles. The body can make vitamin D when it is exposed to sunlight. The ultraviolet rays in sunlight convert a substance in the skin called 7-dehydrocholesterol into vitamin D3.

The other options are incorrect.

  • Option A is incorrect because resistance power does not increase with exposure to sunlight. In fact, too much exposure to sunlight can weaken the immune system.
  • Option B is incorrect because infrared light does not kill bacteria.
  • Option D is incorrect because the pigment cells in the skin do not get stimulated and produce a healthy tan with exposure to sunlight. A tan is the body’s way of protecting itself from the sun’s harmful rays.