Skin flora tends to be most concentrated in particular areas, including:

First of all, you need to know what the term skin flora refers to. Skin flora refers to various bacteria and microbes which live on our bodies or inside of them. They are found all over our bodies, however, there are particular areas where their concentration is higher. For example, this is the case with hands, perineal area, groin, armpits, trunk, and arms. 

3. i would say one, but one is not prime nor composite.