Here's why:

* Carbohydrates are made up of simple sugar units called monosaccharides. These monosaccharides can be linked together to form larger structures like disaccharides (two sugar units) and polysaccharides (many sugar units). Examples include glucose, fructose, and starch.

Let's look at the other macromolecules:

* Proteins are made of amino acids.

* Lipids (fats and oils) are made of fatty acids and glycerol.

* Nucleic acids (DNA and RNA) are made of nucleotides, which contain a sugar, a phosphate group, and a nitrogenous base.