The correct answer is option 4, the sublimation of iodine.

Let`s dissect each option to understand why option 4 is the correct answer.

Option 1: Digestion of food is a biological process that occurs in the human body. It involves the breakdown of food into smaller molecules that can be absorbed and used by the body. This is not a physical process.

Option 2: Corrosion or rusting of a metal is a chemical process. It occurs when metals react with oxygen and water in the environment, leading to the formation of rust. This is not a physical process.

Option 3: The production of hydrogen from an acid is a chemical process. It involves a reaction between an acid and a metal, resulting in the release of hydrogen gas. This is not a physical process.

Option 4: The sublimation of iodine is a physical process. Sublimation is the phase transition in which a substance changes directly from a solid to a gas without passing through the liquid state. In the case of iodine, solid iodine crystals can sublimate when heated, forming purple-colored iodine vapor. This is a physical process.

Therefore, out of the given options, option 4, the sub