On adding ${\mathrm{AgNO}}_3$ solution into $\mathrm{KI}$ solute, a positively charged colloidal sol is obtained when they are in:

$200 \mathrm{ml} \mathrm{of} 0.2 \mathrm{M} {\mathrm{AgNO}}_3 + 200 \mathrm{ml} \mathrm{of} 0.2 \mathrm{M} \mathrm{KI}$

$100 \mathrm{ml} \mathrm{of} 0.1 \mathrm{M} {\mathrm{AgNO}}_3 + 100 \mathrm{ml} \mathrm{of} 0.15 \mathrm{M} \mathrm{KI}$

$100 \mathrm{ml} \mathrm{of} 0.15 \mathrm{M} {\mathrm{AgNO}}_3 + 100 \mathrm{ml} \mathrm{of} 0.1 \mathrm{M} \mathrm{KI}$

$100 \mathrm{ml} \mathrm{of} 0.1 \mathrm{M} {\mathrm{AgNO}}_3 + 50 \mathrm{ml} \mathrm{of} 0.2 \mathrm{M} \mathrm{KI}$