Anaphylaxis can occur due to exposure to which of the following?

B is the correct choice because anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur in response to certain allergens. The most common triggers for anaphylaxis include foods such as peanuts and shellfish, insect stings like those from bees, and medications. These substances can cause the immune system to react in an exaggerated manner, leading to symptoms such as difficulty breathing, swelling, hives, and a drop in blood pressure.

In contrast, polluted air is not typically a direct cause of anaphylactic reactions; while it can exacerbate existing respiratory conditions, it does not usually trigger a systemic allergic response. Excessive exercise can sometimes lead to a form of anaphylaxis known as exercise-induced anaphylaxis, but this condition is uncommon and typically requires other factors, such as eating specific foods prior to exercising. Lastly, although certain medications can cause anaphylactic reactions, saying "certain medications only" is too narrow, as it excludes the broader range of allergens like foods and insect stings, which are significant triggers.