Final answer:
Fc receptors on mast cells specifically bind IgE immunoglobulins, which upon encountering their specific allergen, lead to mast cell degranulation and allergic reactions. Option B.
Step-by-step explanation:
The Fc receptors for mast cells are present for IgE. IgE is important in the body's defense against parasitic infections and is critical in allergic responses, including anaphylaxis. Upon first exposure to an allergen, IgE production is stimulated, and these antibodies bind to mast cells via their Fc region.
In individuals with allergies, allergen-specific IgE molecules are bound to their mast cells. When re-exposed to the same allergen, cross-linking of the surface-bound IgE triggers mast cell degranulation, releasing inflammatory mediators that cause allergic symptoms. So option E.