What type of reaction joins two monosaccharides to form a disaccharide?

The process that joins two monosaccharides to form a disaccharide is known as dehydration synthesis. This reaction involves the removal of a water molecule as the two monosaccharides come together. Specifically, an -OH group from one monosaccharide combines with an -H from the other, resulting in the release of water (H2O) and forming a covalent bond known as a glycosidic linkage between the two sugar units.

Dehydration synthesis is a critical reaction in biochemical processes, as it allows for the construction of larger carbohydrates from smaller units. A familiar example of this is the formation of sucrose from glucose and fructose.

The other options represent different types of reactions: hydrolysis involves the addition of water to break down compounds, fermentation is a biological process that converts sugars into acids, gases, or alcohol, and oxidation refers to the loss of electrons or an increase in oxidation state. These processes do not involve the synthesis of disaccharides from monosaccharides.