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.

Q: Passage: Sichuan came under the firm control of a Chinese central government during the Sui dynasty, but it was during the subsequent Tang dynasty where Sichuan regained its previous political and cultural prominence for which it was known during the Han. Chengdu became nationally known as a supplier of armies and the home of Du Fu, who is sometimes called China's greatest poet. During the An Lushan Rebellion (755-763), Emperor Xuanzong of Tang fled from Chang'an to Sichuan. The region was torn by constant warfare and economic distress as it was besieged by the Tibetan Empire.

A: Who regained their prominence under the Sui dynasty?
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Q: Passage: Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it. It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.

A: What can be used to make glass less dense?
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Q: Passage: Northwestern has roughly 225,000 alumni in all branches of business, government, law, science, education, medicine, media, and the performing arts. Among Northwestern's more notable alumni are U.S. Senator and presidential candidate George McGovern, Nobel Prize–winning economist George J. Stigler, Nobel Prize–winning novelist Saul Bellow, Pulitzer Prize–winning composer and diarist Ned Rorem, the much-decorated composer Howard Hanson, Deputy Prime Minister of Turkey Ali Babacan, the historian and novelist Wilma Dykeman, and the founder of the presidential prayer breakfast Abraham Vereide. U.S. Supreme Court Associate Justice John Paul Stevens, Supreme Court Justice and Ambassador to the United Nations Arthur Joseph Goldberg, and Governor of Illinois and Democratic presidential candidate Adlai Stevenson are among the graduates of the Northwestern School of Law. Many Northwestern alumni play or have played important roles in Chicago and Illinois, such as former Illinois governor and convicted felon Rod Blagojevich, Chicago Bulls and Chicago White Sox owner Jerry Reinsdorf, and theater director Mary Zimmerman. Northwestern alumnus David J. Skorton currently serves as president of Cornell University. Rahm Emanuel, the mayor of Chicago and former White House Chief of Staff, earned a Masters in Speech and Communication in 1985.

A:
Which of Southwestern's alumni is notable for becoming a U.S. Senator and presidential candidate?
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