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.
--------
Question: Passage: The South Saharan steppe and woodlands ecoregion is a narrow band running east and west between the hyper-arid Sahara and the Sahel savannas to the south. Movements of the equatorial Intertropical Convergence Zone (ITCZ) bring summer rains during July and August which average 100 to 200 mm (3.9 to 7.9 in) but vary greatly from year to year. These rains sustain summer pastures of grasses and herbs, with dry woodlands and shrublands along seasonal watercourses. This ecoregion covers 1,101,700 km2 (425,400 mi2) in Algeria, Chad, Mali, Mauritania, and Sudan.

Answer: what ecoregion runs north and south in a norrow band?

Question: Passage: A fine tribute to the fall of Warsaw and history of Poland can be found in the Warsaw Uprising Museum and in the Katyn Museum which preserves the memory of the crime. The Warsaw Uprising Museum also operates a rare preserved and operating historic stereoscopic theatre, the Warsaw Fotoplastikon. The Museum of Independence preserves patriotic and political objects connected with Poland's struggles for independence. Dating back to 1936 Warsaw Historical Museum contains 60 rooms which host a permanent exhibition of the history of Warsaw from its origins until today.

Answer: Where can a tribute to the fall of Katyn be found?

Question: Passage: The physicians of the Yuan court came from diverse cultures. Healers were divided into non-Mongol physicians called otachi and traditional Mongol shamans. The Mongols characterized otachi doctors by their use of herbal remedies, which was distinguished from the spiritual cures of Mongol shamanism. Physicians received official support from the Yuan government and were given special legal privileges. Kublai created the Imperial Academy of Medicine to manage medical treatises and the education of new doctors. Confucian scholars were attracted to the medical profession because it ensured a high income and medical ethics were compatible with Confucian virtues.

Answer:
Who were potachi?