Final answer:
The leading cause of fatal or near-fatal food allergic reactions in the US each year is peanuts. They can cause anaphylaxis, which is a severe allergic reaction requiring immediate medical attention.
Step-by-step explanation:
The food that is the leading cause of fatal or near-fatal food allergic reactions in the United States each year is C. Peanut. Food allergies trigger the immune system to react to certain foods as if they were dangerous, even though they are typically harmless. Common allergenic foods include nuts, shellfish, grains, milk, and eggs. A severe allergic reaction, known as anaphylaxis, can be triggered by foods like peanuts, and without emergency medical treatment, it can lead to death. Peanuts are particularly notorious for causing these severe reactions, even in very small amounts, therefore it is critical for those with peanut allergies to strictly avoid them and be prepared with emergency medication like epinephrine auto-injectors.