Disaccharides are carbohydrates composed of two monosaccharide units joined together by a glycosidic bond. They are commonly found in various foods and play an important role in providing energy to the body. Among the given options, trehalose is the correct answer as it is a disaccharide.

Explanation:

Trehalose:
- Trehalose is a disaccharide composed of two glucose molecules joined together by an α,α-1,1-glycosidic bond.
- It is found in various organisms such as bacteria, fungi, plants, and invertebrates.
- Trehalose serves as a storage carbohydrate and can be broken down into glucose molecules when energy is needed.
- It is often used as a food additive and can be found in products such as desserts, beverages, and processed foods.

Inulin:
- Inulin is a polysaccharide, not a disaccharide.
- It is composed of a chain of fructose molecules joined by β-2,1-glycosidic bonds.
- Inulin is found in various plants, particularly in the roots or tubers.
- It serves as a storage carbohydrate and can be broken down into fructose molecules for energy.

Raffinose:
- Raffinose is a trisaccharide, not a disaccharide.
- It is composed of one glucose molecule, one galactose molecule, and one fructose molecule.
- Raffinose is found in various plants, particularly in seeds and legumes.
- It serves as a storage carbohydrate and can be broken down into its constituent monosaccharides for energy.

Cellulose:
- Cellulose is a polysaccharide, not a disaccharide.
- It is composed of a chain of glucose molecules joined by β-1,4-glycosidic bonds.
- Cellulose is the main component of plant cell walls and provides structural support.
- It cannot be digested by humans due to the lack of enzymes to break down the β-1,4 glycosidic bonds.

Conclusion:
Among the given options, trehalose is the correct answer as it is a disaccharide composed of two glucose molecules. Inulin, raffinose, and cellulose are polysaccharides with different compositions and functions.