Answer:
improper disposal of sewage
Answer: Serotonin
Explanation:
Serotonin is an hormone, derived from the amino acid, tryptothan. It is involved in vasodilation, sleep regulation, mood changes, capillary permeability, and causes contraction of smooth muscles like that of the stomach to signal hunger.
Tge system that coirdinate and send message to the body is the nervous system
<span>Having standard written research protocols is the correct answer. ;)</span>