Final answer:
Corn has the lowest niacin bioavailability among the provided options because it contains niacytin, a form of niacin that is not easily absorbed by the human body.
Step-by-step explanation:
The food listed below with the lowest niacin bioavailability is B. corn. Niacin, also known as vitamin B3, is an essential nutrient found in various foods. Some sources of niacin include liver, fish, beans, and peanuts. Niacin can also be created in the human body from the amino acid tryptophan. It is important to note that while foods like almonds, spinach, milk, and organ meats are good sources, corn contains niacytin, a form of niacin that is not readily absorbed by the human body. Additionally, grains such as wheat can have varying levels of niacin bioavailability depending on whether they are processed or whole. Nevertheless, corn generally has a lower bioavailability of niacin compared to the other options listed.