The correct option is B 0.685 N
Normality=number of gram equivalentstotal volume of the solution in L
Number of gram equivalents of HCl = 0.5
Mass of HCl in solution =0.5×36.5=18.25 g
Mass of HCl remaining =18.25–3.25=15 g
Number of gram equivalents of HCl =1536.5
New volume =0.6 L
New normality 15/36.50.6=0.685 N