This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Input: Consider Input: Passage: The Rhine was not known to Herodotus and first enters the historical period in the 1st century BC in Roman-era geography. At that time, it formed the boundary between Gaul and Germania. The Upper Rhine had been part of the areal of the late Hallstatt culture since the 6th century BC, and by the 1st century BC, the areal of the La Tene culture covered almost its entire length, forming a contact zone with the Jastorf culture, i.e. the locus of early Celtic-Germanic cultural contact. In Roman geography, the Rhine formed the boundary between Gallia and Germania by definition; e.g. Maurus Servius Honoratus, Commentary on the Aeneid of Vergil (8.727) (Rhenus) fluvius Galliae, qui Germanos a Gallia dividit "(The Rhine is a) river of Gaul, which divides the Germanic people from Gaul."

Output: When did Herodotus discover the Rhine?

Input: Consider Input: Passage: The Low German varieties spoken in Germany are often counted among the German dialects. This reflects the modern situation where they are roofed by standard German. This is different from the situation in the Middle Ages when Low German had strong tendencies towards an ausbau language.

Output: What is often not included when counting German dialects?

Input: Consider Input: Passage: High-voltage AC overhead systems are not only for standard gauge national networks. The meter gauge Rhaetian Railway (RhB) and the neighbouring Matterhorn Gotthard Bahn (MGB) operate on 11 kV at 16.7 Hz frequency. Practice has proven that both Swiss and German 15 kV trains can operate under these lower voltages. The RhB started trials of the 11 kV system in 1913 on the Engadin line (St. Moritz-Scuol/Tarasp). The MGB constituents Furka-Oberalp-Bahn (FO) and Brig-Visp-Zermatt Bahn (BVZ) introduced their electric services in 1941 and 1929 respectively, adopting the already proven RhB system.
Output: Low-voltage AC overhead systems are not only for what?