Here's why:

* True roots are typically thin, fibrous structures responsible for anchoring the plant and absorbing water and nutrients.

* Stems are generally above ground, supporting leaves and flowers. However, some stems are modified for specialized purposes, such as storage.

* Carrots are fleshy, swollen taproots, which are actually the hypocotyl, the part of the stem connecting the root and the cotyledon (seed leaves). This hypocotyl is modified for storing carbohydrates, giving the carrot its characteristic shape and nutritional value.

Therefore, while carrots grow underground, they are not true roots but modified stems.