Lake Constance consists of three bodies of water: the Obersee ("upper lake"), the Untersee ("lower lake"), and a connecting stretch of the Rhine, called the Seerhein ("Lake Rhine"). The lake is situated in Germany, Switzerland and Austria near the Alps. Specifically, its shorelines lie in the German states of Bavaria and Baden-Württemberg, the Austrian state of Vorarlberg, and the Swiss cantons of Thurgau and St. Gallen. The Rhine flows into it from the south following the Swiss-Austrian border. It is located at approximately 47°39′N 9°19′E﻿ / ﻿47.650°N 9.317°E﻿ / 47.650; 9.317.
Which of the following is not a Swiss canton: Thurgau, Bavaria or St. Gallen?