Which of the following is a Native American tribe in the United States?

The Sioux is indeed a Native American tribe in the United States, known for its rich history, culture, and significant impact on American history. The Sioux people traditionally inhabited regions in the northern Great Plains. They are composed of three major divisions: the Dakota, Lakota, and Nakota, each with its own dialects and cultural practices. The Sioux played a crucial role in various historical events, including the battles against U.S. expansion in the 19th century, and they continue to be a prominent cultural influence today.

In contrast, the other options mentioned refer to groups that are not Native American tribes. The Irish refers to the people of Ireland, Bavarian pertains to a region in Germany, and Mongolian describes the people of Mongolia in East Asia. These groups have their own distinct cultures and histories separate from the Native American tribes in the United States.