First notice the words “not a”.
The question works in reverse: you must not select one of the three actual federal states, but the name that does not belong. The words “not a” change the entire selection task.
Compound names are not a reliable distinguishing feature. All the offered names contain several parts. The present list of Länder is more useful: it explicitly includes the other three answers.
The other three answers
These three names really are federal states, so they are not the answer.
North Rhine-Westphalia
North Rhine-Westphalia is one of the sixteen Länder. Precisely because it is a federal state, it does not answer the negative question.
Mecklenburg-Western Pomerania
Mecklenburg-Western Pomerania is named as a Land in the preamble. Its long compound name does not change that.
Saxony-Anhalt
Saxony-Anhalt is also a federal state in its own right. Do not confuse it with the separate Land of Saxony.
Separate present Länder lists from historical names.
A geographical name can appear in history books or regional contexts without naming a German federal state today. This question concerns the present Federal Republic, not every earlier political affiliation.
You do not need to redraw a border or assess a historical territorial question here. The verifiable distinction is narrower: which names appear on today’s list of Länder?
Preamble · Basic Law ↗“Not a federal state” → Alsace-Lorraine.
Check the negative wording and compare the name with the present list.
Three words for this question
- keinnot a / no
- Denies that something belongs to the stated group.
- das Verzeichnislist / register
- An ordered list, here of the Länder.
- die Regionregion
- A geographical area, not automatically a federal state.