Question

a polysaccharide is a type of polymer. polymers are molecules made of many—often hundreds or thousands—of repeating units called monomers. in polysaccharides, the monomers are simple sugars like glucose, fructose, or galactose. some polysaccharides have only one type of monomer, while other polysaccharides have two or more different types of monomers.
select the polysaccharide.

Explanation:

A polysaccharide is a polymer (many repeating units, monomers). The first structure has two sugar units (oligomer, maybe disaccharide), the second is a single sugar (monomer, monosaccharide), and the third has many repeating sugar - like units (matches polymer definition of polysaccharide).

Answer:

The third structure (the one with multiple repeating sugar - like monomer units) is the polysaccharide.