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: External evidence is evidence of each physical witness, its date, source, and relationship to other known witnesses. Critics will often prefer the readings supported by the oldest witnesses. Since errors tend to accumulate, older manuscripts should have fewer errors. Readings supported by a majority of witnesses are also usually preferred, since these are less likely to reflect accidents or individual biases. For the same reasons, the most geographically diverse witnesses are preferred. Some manuscripts show evidence that particular care was taken in their composition, for example, by including alternative readings in their margins, demonstrating that more than one prior copy (exemplar) was consulted in producing the current one. Other factors being equal, these are the best witnesses. The role of the textual critic is necessary when these basic criteria are in conflict. For instance, there will typically be fewer early copies, and a larger number of later copies. The textual critic will attempt to balance these criteria, to determine the original text.

Output: External evidence is evidence of each physical witness, its date, source, relationship to other known witnesses, and what else? 


Input: Consider Input: Passage: The 5th Dalai Lama is known for unifying the Tibetan heartland under the control of the Gelug school of Tibetan Buddhism, after defeating the rival Kagyu and Jonang sects and the secular ruler, the Tsangpa prince, in a prolonged civil war. His efforts were successful in part because of aid from Güshi Khan, the Oirat leader of the Khoshut Khanate. With Güshi Khan as a largely uninvolved overlord, the 5th Dalai Lama and his intimates established a civil administration which is referred to by historians as the Lhasa state. This Tibetan regime or government is also referred to as the Ganden Phodrang.

Output: Who is known for unifying the Tibetan heartland under the control of Kagyu?


Input: Consider Input: Passage: Germanic tribes crossed the Rhine in the Migration period, by the 5th century establishing the kingdoms of Francia on the Lower Rhine, Burgundy on the Upper Rhine and Alemannia on the High Rhine. This "Germanic Heroic Age" is reflected in medieval legend, such as the Nibelungenlied which tells of the hero Siegfried killing a dragon on the Drachenfels (Siebengebirge) ("dragons rock"), near Bonn at the Rhine and of the Burgundians and their court at Worms, at the Rhine and Kriemhild's golden treasure, which was thrown into the Rhine by Hagen.


Output: When did the "Germanic Heroic Age" end?