root
a root
An uncooked sweet potato should be very firm or hard. Soft ones have either started to dry out or could be rotting.
No, we just discussed this in our bio class its actually a tuberous root, not to be confused with the term tuber. Potatoes on the other hand are stems, but there is a difference.
No. Although the potato is grown underground, it is grown from underground roots and it is not undeground stems.