Choose the correct answer from the options given below :

We first recall the constituting units of the given carbohydrates.

Disaccharides and polysaccharides are identified by the monosaccharide units that build them up and by the nature of the glycosidic linkages joining those units.

Case A: Sucrose
Sucrose is made up of one $$\alpha$$-D-glucose unit and one $$\beta$$-D-fructose unit joined through an $$\alpha,\,\beta\,(1\rightarrow2)$$ glycosidic bond. Hence the correct description for sucrose is “$$\alpha$$-D-glucose + $$\beta$$-D-fructose”. This corresponds to Item (III).

Case B: Lactose
Lactose consists of $$\beta$$-D-galactose and $$\beta$$-D-glucose connected by a $$\beta\,(1\rightarrow4)$$ linkage. Therefore its description is “$$\beta$$-D-galactose + $$\beta$$-D-glucose”, i.e. Item (IV).

Case C: Maltose
Maltose is formed when two $$\alpha$$-D-glucose molecules combine through an $$\alpha\,(1\rightarrow4)$$ bond. Thus the correct description is “two $$\alpha$$-D-glucose units”, namely Item (II).

Case D: Cellulose
Cellulose is a long-chain polysaccharide composed solely of $$\beta$$-D-glucose units linked by repeated $$\beta\,(1\rightarrow4)$$ glycosidic bonds. Hence its description is “polymer of $$\beta$$-D-glucose”, which is Item (I).

Collecting the matches:

$$\text{(A) Sucrose} \rightarrow \text{(III)}$$
$$\text{(B) Lactose} \rightarrow \text{(IV)}$$
$$\text{(C) Maltose} \rightarrow \text{(II)}$$
$$\text{(D) Cellulose} \rightarrow \text{(I)}$$

This ordering is exactly the combination given in Option B.

Final answer: Option B which is: (A)-(III), (B)-(IV), (C)-(II), (D)-(I)