The sol given below with negatively charged colloidal particles is:
\( \mathrm{AgNO_3} \) added to \( \mathrm{KI} \) solution
\( \mathrm{KI} \) added to \( \mathrm{AgNO_3} \) solution
\( \mathrm{Al_2O_3 \cdot xH_2O} \) in water
\( \mathrm{FeCl_3} \) added to hot water