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.
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Question: Passage: As the initial punk movement dwindled, vibrant new scenes began to coalesce out of a variety of bands pursuing experimental sounds and wider conceptual territory in their work. Many of these artists drew on backgrounds in art and viewed their music as invested in particular political or aesthetic agendas. British music publications such as the NME and Sounds developed an influential part in this nascent post-punk culture, with writers like Jon Savage, Paul Morley and Ian Penman developing a dense (and often playful) style of criticism that drew on critical theory, radical politics and an eclectic variety of other sources.

Answer: What happened as the pot-punk movement dwindled?

Question: Passage: Conventional bleaching of wood pulp using elemental chlorine produces and releases into the environment large amounts of chlorinated organic compounds, including chlorinated dioxins. Dioxins are recognized as a persistent environmental pollutant, regulated internationally by the Stockholm Convention on Persistent Organic Pollutants. Dioxins are highly toxic, and health effects on humans include reproductive, developmental, immune and hormonal problems. They are known to be carcinogenic. Over 90% of human exposure is through food, primarily meat, dairy, fish and shellfish, as dioxins accumulate in the food chain in the fatty tissue of animals.

Answer: What does bleaching of meat release into the environment?

Question: Passage: Houston was the headquarters of Continental Airlines until its 2010 merger with United Airlines with headquarters in Chicago; regulatory approval for the merger was granted in October of that year. Bush Intercontinental became United Airlines' largest airline hub. The airline retained a significant operational presence in Houston while offering more than 700 daily departures from the city. In early 2007, Bush Intercontinental Airport was named a model "port of entry" for international travelers by U.S. Customs and Border Protection.

Answer:
Until 2010, which airline made Texas its headquarters?