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.

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.
Who regained their prominence under the Sui dynasty?

Passage: About 75% of the population is employed in subsistence agriculture upon Swazi Nation Land (SNL). In contrast with the commercial farms, Swazi Nation Land suffers from low productivity and investment. This dual nature of the Swazi economy, with high productivity in textile manufacturing and in the industrialised agricultural TDLs on the one hand, and declining productivity subsistence agriculture (on SNL) on the other, may well explain the country's overall low growth, high inequality and unemployment.
Where does the population get 75% of its income?

Passage: To help reduce consumption, in 1974 a national maximum speed limit of 55 mph (about 88 km/h) was imposed through the Emergency Highway Energy Conservation Act. Development of the Strategic Petroleum Reserve began in 1975, and in 1977 the cabinet-level Department of Energy was created, followed by the National Energy Act of 1978.[citation needed] On November 28, 1995, Bill Clinton signed the National Highway Designation Act, ending the federal 55 mph (89 km/h) speed limit, allowing states to restore their prior maximum speed limit.

What was imposed on November 28 1995 by the Emergency Highway Energy Conservation Act?