What enity is the strongest oxidizing agent? what enity is the strongest reducing agent?

H20(l), K^+(aq), I^-(aq), C(s)

The strongest oxidizing agent is K+ (potassium ion). This is because it readily attracts electrons from other species during a redox reaction, leading to oxidation.

The strongest reducing agent is C (carbon in its solid form). Carbon has a strong tendency to donate electrons, and therefore can easily reduce other species by losing electrons itself during a redox reaction.