Task: Question Answering
Input (English): Question: In IgE-mediated hypersensitivity reactions: 
 Options:  <1> Eosinophils and mast cells play an important role. <2> There are no cellular elements involved. <3> Antibody-mediated cytotoxicity reactions play a key role. <4> There are no elements of the immune system involved in atopy. <5> The IgE immunoglobulin receptor does not intervene.
Output (English): 1