Which of the following locations is it illegal to carry a concealed firearm in South Dakota, even with a permit?

In South Dakota, it is illegal to carry a concealed firearm in courthouses, even with a permit. Courthouses are considered high-security areas where firearms are prohibited to maintain safety and order within the judicial system. It is important for individuals to be aware of these restricted locations to ensure they are in compliance with the law and avoid potential legal consequences.

Options A, B, and C are not correct because in South Dakota, individuals with a valid concealed carry permit are generally allowed to carry concealed firearms in state parks, private properties posted with 'No Concealed Weapons' signs (unless requested to leave by the owner or person in control of the property), and in restaurants serving alcohol unless specifically prohibited by the establishment.