Step 1: This question asks for the scientific term for substances that trigger an allergic reaction. This is based on the chapter "Allergy".
Step 2: An allergy is an exaggerated response by the immune system to a substance that is normally harmless to most people.
Step 3: The specific term for such a substance is an 'allergen'. Common allergens include pollen, dust mites, mold spores, pet dander, and certain foods. Bacteria and viruses cause infections, not typically allergic reactions. The marked answer (B) is incorrect.