This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A type of immediately occurring reaction in which antigens combine with antibodies already attached 
to the surface of mast cells and basophils is called: 
Select and explain. 
A. Type I hypersensitivity, B. Type II hypersensitivity, C. Type III hypersensitivity, D. Type IV hypersensitivity
A: Type I hypersensitivity
Answer: A: Type I hypersensitivity 
Explanation: None