State capital is a specific constitutional role.
The answer does not depend on which town comes to mind first or which landmark you know. The authoritative reference is the state constitution. It identifies Erfurt as capital; no comparison of cities’ fame is needed.
Also distinguish the state level from the local level. The Landtag passes laws for Thüringen and scrutinises the state government. A city council or city administration acts at municipal level. Erfurt being the capital does not make every authority located there an authority for the whole state.
The other three answers
The other place names do not fulfil the role asked for.
Eisenach.
Eisenach is not the state capital. Do not confuse a familiar Thüringen place name with the constitutional answer, Erfurt.
Gera.
Gera is also not the capital identified in Article 44.
Jena.
Jena is not the state capital. The question requires Erfurt, regardless of which other city you know.
State and municipality remain separate levels.
Being the capital does not make Erfurt’s city administration responsible for every Thüringen resident. For a personal administrative matter, the authority’s subject and territorial responsibilities matter.
The question asks for a city name, not a person or population figure. A change in political office does not change the answer to this capital question.
Article 44(4) · Constitution of Thüringen ↗Thüringen → Erfurt.
Distinguish the state capital from county and municipal administrations.
Three words for this question
- die Landeshauptstadtstate capital
- The city designated as the capital of a federal state.
- die Landesebenestate level
- The level of a federal state within Germany.
- zuständigresponsible
- Legally responsible for a particular task.