Influenza and the common cold are infections of the respiratory system digestive system endocrine system reproductive system

How do the uv rays cause damage?   what exactly causes the skin to burn;   can you be more specific about this mechanism?   3. how do photosensitive medications increase a person's sensitivity to sunlight and therefore increase their risk of getting burned?     what kind of medications can increase photo-sensitivity, can you think of some examples?

When exercising, you shouldn’t go past to avoid an injury.

Which food preservation method can people use at home? a. fermentation b. irradiation c. pasteurization d. thermal processing