<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:You are working in the emergency room of a childrens hospital when a 4-year-old girl is brought in by ambulance due to difficulty breathing. The patient had been eating lunch on a school field trip when she suddenly complained of abdominal pain. Shortly thereafter, she was noted to have swelling of the lips, a rapidly developing red rash and difficulty breathing. In the ambulance her blood pressure was persistently 8050 mmHg despite intramuscular epinephrine. In the course of stabilization and work up of the patient, you note an elevated tryptase level. What is the mechanism behind this elevated tryptase level?? A: IgG production by plasma cells, B: IgM mediated complement activation, C: Cross-linking of IgE on mast cells, D: Antibody-antigen immune complexes, E: Cross-linking of IgG on mast cells,  <response>: This is a clinical vignette describing a 4-year-old girl with anaphylaxis likely triggered by food allergy. She has symptoms of lip swelling, rash, hypotension, and difficulty breathing, classic signs of an allergic reaction. The question asks about the mechanism behind her elevated tryptase level. Tryptase is an enzyme released by mast cells during degranulation, which occurs when mast cells are activated through cross-linking of IgE by an allergen. So the elevated tryptase indicates mast cell activation. The correct answer will relate to mast cell degranulation via IgE cross-linking.C: Cross-linking of IgE on mast cells 