Microbes that colonize the skin need to be resistant to salt and ph.

The correct answer is C).high salt and low pH. Sweat glands pump out saline solution as a means of cooling the body as well as removing waste (sweat). Human skin typically has a pH of 5.5-5.9 with major issues at higher or lower pH (e.g., eczema)

It's either -limiting factors or -scarce resources but i'd go with my first answer since the food and water are abundant they really aren't scarce