Your immune system uses a huge army of defender cells - different types of white blood cell. You make about 1000 million of them every day in your bone marrow. Some of these cells, called macrophages, constantly patrol your body, destroying germs as soon as they enter. This is your 'natural' or inborn immunity. But if an infection begins to take hold, your body fights back with an even more powerful defence of T- and B-cells. They give you acquired immunity, so that the same germ can never make you as ill again.
It help warm and moisten incoming air
I think the human behavior is free
Sunburn is caused by too much exposure to ultraviolet (UV) light. UV light may be from sunlight or artificial sources, such as sunlamps and tanning beds. Melanin is the dark pigment in the skin's outer layer that gives skin its normal color
Hope I helped
Answer:
he simply means he should try harder and probably he is not feeling well
