Task: Question Answering
Input (English): Question: Point out the correct answer regarding B lymphocytes. 
 Options:  <1> Its two main subpopulations are called B-helper and B-cytotoxic. <2> They are the cells responsible for the production of antibodies in the rejection of an autologous transplant of hematopoietic progenitors. <3> They are the target cells of the anti-CD20 monoclonal antibody (rituximab). <4> They require co-stimulation CD20-CD19 for the expression of the CD3 molecule on its surface. <5> It is the type of majority lymphocyte in the peripheral blood of patients with Bruton's disease.
Output (English): 3