The correct option is A positively charged sol
On treatment of AgNO3 with KI solution, AgI is formed.
AgNO3 + KI → AgI + KNO3
As an excess of AgNO3 is taken, it also exists in its dissociated form as follows,
AgNO3→Ag+ + NO3−
These Ag+ ions are adsorbed on AgI and [AgI]Ag+ are formed. Thus, the colloidal particles acquire a positive charge.