Which mixture of the solutions will lead to the formation of negatively charged colloidal [AgI]I– sol ?

Excess KI results in negative sol         AgNO3               KI    (1) 0.1 moles          0.075moles            (2) 0.05 moles         0.075moles (3) 0.05 moles         0.1 moles In (2) & (3) KI is excess , so AgI ppt. preferentially adsorbs I-  from KI to form a negative sol