Answer:
A. Bacteria.
Step-by-step explanation:
Food poisoning refers to illness caused by eating contaminated food, which is not that bad, within few days, people can get better without treatment. It can be caused by many organisms source of infection, however, most of the cases of food poisoning is caused by bacteria, salmonella is a common example, which can be ingested from food that's not well cooked, below the proper temperature. Another common bacterias which cause this contaminations are E. coli and Listeria,
Actually, according to Centers of Disease Control and Prevention, around 1,000,000 cases per year of food poisoning are caused by salmonella. In addition, the most common symptoms of food poisoning are nausea, vomiting and diarrhea.
Therefore, the right choice is A.