Question

Sucrose and lactose are disaccharides that have the same chemical formula, C12H22O11. However, these sugars have different characteristics and behave differently in chemical reactions. Which of the following generalizations can explain this?
Disaccharides are used for different cellular processes, and they only take part in reactions in which they are needed.

Disaccharides are different in structure because they are not made up of the same monosaccharides, and this gives them different properties.

Disaccharides are made from the same monosaccharides, but the monosaccharides are arra

Answer 1

The answer is Disaccharides are different in structure because they are not made up of the same monosaccharides, and this gives them different properties.

Both sucrose and lactose are disaccharides, however, they are made up different monosaccharides:
Disaccharide = monosaccharide + monosaccharide
Sucrose = glucose + fructose
Lactose = glucose + galactose 

Since they have different structures, their characteristics and behaviour in chemical reactions must differ, too.