Which of the following group of tribes is not part of the Sioux Nation?

The Great Sioux Nation can be divided into three distinct groups based on the language and geography; Dakota (Santee, Eastern Dakota), Lakota (Teton, Western Dakota) and Nakota (Yankton, Central Dakota). “Dakota” and “Lakota” means “friends” or “allies”.

The Lakota people were a founding group of the seven council fires which consisted of seven tribal bands; four Dakota bands (Mdewakanton, Wahpekute, Wahpeton, Sisseton), two Nakota bands (Yankton, Yanktonai) and a Lakota band (Teton). After the introduction of the horse in the early 18th century, the Sioux dominated larger areas of land—from present-day Central Canada to the Platte River, from Minnesota to the Yellowstone River, including the Powder River country.

The term Nakota is the endonym used by those native peoples of North America who usually go by the name of Assiniboine, in the United States, and of Stoney, in Canada.

Today, the Sioux maintain many separate tribal governments scattered across several reservations, communities, and reserves in North Dakota, South Dakota, Nebraska, Minnesota, and Montana in the United States; and Manitoba, southern Saskatchewan, and Alberta in Canada.