Electrochemical corrosion can occur, only if __________ is present in contact with metal.

ANS:C - liquid medium

In the context of electrochemical corrosion, a liquid medium refers to any medium that allows the flow of ions, typically an aqueous solution such as water or an electrolyte. When a metal is in contact with a liquid medium containing dissolved ions, such as water containing dissolved salts or acids, it creates an environment conducive to electrochemical corrosion. In this medium, the metal can undergo oxidation and reduction reactions, facilitated by the presence of ions. Oxygen dissolved in the liquid medium often plays a crucial role in the corrosion process by participating in reactions that lead to the formation of metal oxides or hydroxides. These reactions can result in the degradation of the metal surface over time, leading to corrosion. Overall, the presence of a liquid medium enhances the electrochemical reactions involved in corrosion, making it a significant factor in the corrosion process.