Mucus traps pathogens, therefore it acts as which kind of barrier? A. chemical

B. physical

20 point reward

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?

Practice or pre-exercise theories of play pose the idea that a. play provides children with an opportunity to practice adult activities. b. play is necessary to reenergize human cognition. c. children have too much energy and play will rid them of that energy. d. children are the link between animals and human beings.

Which is a type of epithelial tissue? a. the skin on your hand b. cardiac muscle c. neurons d. cartilage