Here's why:

* Homopolysaccharide: Made up of only one type of monosaccharide (e.g., starch is made of only glucose).

* Heteropolysaccharide: Made up of two or more different types of monosaccharides.

Agar is composed of two main sugar units:

* Agarose: A linear polymer of D-galactose and 3,6-anhydro-L-galactose.

* Agaropectin: A more complex structure containing D-galactose, 3,6-anhydro-L-galactose, and other sugars like L-galactose, D-glucuronic acid, and sulfate groups.

Since agar contains multiple different sugar units, it qualifies as a heteropolysaccharide.