Final answer:
D. Norovirus
Norovirus is the leading cause of food-borne illnesses in the United States, with Salmonella being a significant bacterial contributor to these illnesses.
Step-by-step explanation:
The leading cause of food-borne illnesses in the United States is Norovirus. Among bacteria, Salmonella is notably dangerous and found in various foods including raw and undercooked meat, poultry, dairy products, and seafood. While Escherichia coli (E. coli) and Campylobacter are significant contributors to foodborne illnesses as well, they are not the leading cause. The top five pathogens that lead to food-related sickness include Norovirus, Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus (Staph).