The correct answer is option 3, glucose.

Cellulose is a complex carbohydrate that makes up the primary structural component of plant cell walls. It is composed of repeating units of glucose molecules bonded together. Glucose is a monosaccharide, which means it is a simple sugar. It is the most common form of sugar found in living organisms and is used by cells as an energy source.

Option 1, fructose, is also a monosaccharide but is not a component of cellulose. Fructose is commonly found in fruits and is often referred to as fruit sugar.

Option 2, galactose, is another monosaccharide that is not a component of cellulose. Galactose is found in the disaccharide lactose, which is commonly found in milk.

Option 4, maltose, is a disaccharide composed of two glucose molecules bonded together. While glucose is a component of cellulose, maltose itself is not found in cellulose.

In summary, cellulose is made up of repeating units of the monosaccharide glucose, which is option 3.