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: Han Chinese make up the vast majority of the population, and the largest Han subgroup are the speakers of Wu varieties of Chinese. There are also 400,000 members of ethnic minorities, including approximately 200,000 She people and approximately 20,000 Hui Chinese[citation needed]. Jingning She Autonomous County in Lishui is the only She autonomous county in China.
[A]: What kind of Japanese make up the vast majority of the population?


[Q]: Passage: BSkyB utilises the VideoGuard pay-TV scrambling system owned by NDS, a Cisco Systems company. There are tight controls over use of VideoGuard decoders; they are not available as stand-alone DVB CAMs (conditional-access modules). BSkyB has design authority over all digital satellite receivers capable of receiving their service. The receivers, though designed and built by different manufacturers, must conform to the same user interface look-and-feel as all the others. This extends to the Personal video recorder (PVR) offering (branded Sky+).
[A]: What is the name of the TV scrambling system BSkyB couldn't use?


[Q]: Passage: The abbey's two western towers were built between 1722 and 1745 by Nicholas Hawksmoor, constructed from Portland stone to an early example of a Gothic Revival design. Purbeck marble was used for the walls and the floors of Westminster Abbey, even though the various tombstones are made of different types of marble. Further rebuilding and restoration occurred in the 19th century under Sir George Gilbert Scott.
[A]:
When were the eastern towers built?