5. What contaminate is responsible for most foodborne illness? *

I can see that there are no choices, so I'll answer the question according to my understanding.

Norovirus

Explanation:

Foodborne illness is a type of illness that one gets after consuming contaminated food or drinks. The biological contaminant may be a virus, bacteria, parasites and other pathogens. This mostly happens through improper handling or preservation of food. A person with this illness may experience symptoms of diarrhea, vomiting, nausea, etc.

The most common biological contaminant that causes foodborne illness is the "norovirus." This is said to be mild in nature, but may also cause some deaths.