What are diseases such as a strep throat and Athlete’s foot caused by?
miasma
decaying matter
microorganisms
temperature changes

c. Microorganisms

Explanation:

Microorganism are the microscopic organisms present in environment such as bacteria, fungi and virus.

Strep throat is a infection of throat caused by a "Group A Streptococcus bacterium". The diseases of strep throat causes large red patches on the skin. some of the symptoms of strep throat include fevers, chills and blisters.

Athlete's foot is a feet infection caused by different fungi such as trichophyton, microsporum and epidermophyton. Symptoms of Athlete's foot include scaling, itching, redness and cracking.

Hence, the correct option is c.

when it is at an intermediate population density