The odd one out in the given options is 'c) Sand'.

Explanation:

- Sugar: Sugar is a sweet-tasting substance that is commonly used as a sweetener in various food and beverage preparations. It is derived from sugarcane or sugar beets and is composed of sucrose molecules. Sugar is soluble in water and has a granulated or powdered form.

- Salt: Salt is a crystalline mineral composed primarily of sodium chloride. It is commonly used for seasoning and preserving food and is also an essential nutrient for the human body. Salt is soluble in water and has a granulated or powdered form.

- Sand: Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is primarily made up of silica, which is a compound of silicon and oxygen. Sand is commonly found in deserts, beaches, and riverbeds. Unlike sugar and salt, sand is not soluble in water and does not have a granulated or powdered form.

- Milk Powder: Milk powder is a dehydrated form of milk, obtained by evaporating the water content from liquid milk. It is commonly used as a convenient alternative to liquid milk, especially in situations where refrigeration is not available or for extended shelf life. Milk powder is soluble in water and forms a liquid when reconstituted.

Based on the characteristics mentioned above, the odd one out is 'c) Sand' because it is not a soluble substance like sugar, salt, and milk powder. Additionally, sand is a naturally occurring material while the other options are processed or derived from specific sources.