This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
A superantigen is a bacterial product that - 
Select and explain. 
A. Binds to B7 and CD28 costimulatory molecules, B. Binds to the beta chain of TCR and MHC class II molecules of APC stimulating T cell activation, C. Binds to the CD4+ molecule causing T cell activation, D. Is presented by mactrophages to a larger-than-normal number of T helper CD4 + lumphocytes
B: Binds to the beta chain of TCR and MHC class II molecules of APC stimulating T cell activation
Answer: B: Binds to the beta chain of TCR and MHC class II molecules of APC stimulating T cell activation 
Explanation: Superantigens are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. Superantigens bind first to the MHC Class II and then coordinate to the variable alpha or beta chain of T-cell Receptors . Reff: Ananthanarayan & Panikers textbook of microbiology 9th edition pg:90