instruction:
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: From the 19th century, there was a revival in many ancient glass-making techniques including cameo glass, achieved for the first time since the Roman Empire and initially mostly used for pieces in a neo-classical style. The Art Nouveau movement made great use of glass, with René Lalique, Émile Gallé, and Daum of Nancy producing colored vases and similar pieces, often in cameo glass, and also using luster techniques. Louis Comfort Tiffany in America specialized in stained glass, both secular and religious, and his famous lamps. The early 20th-century saw the large-scale factory production of glass art by firms such as Waterford and Lalique. From about 1960 onwards there have been an increasing number of small studios hand-producing glass artworks, and glass artists began to class themselves as in effect sculptors working in glass, and their works as part fine arts.
answer:
What famous lampmaker used factory production?


question:
Passage: Even though some proofs of complexity-theoretic theorems regularly assume some concrete choice of input encoding, one tries to keep the discussion abstract enough to be independent of the choice of encoding. This can be achieved by ensuring that different representations can be transformed into each other efficiently.
answer:
What can not be achieved by ensuring different representations can transformed into each other efficiently?


question:
Passage: In a career spanning more than four decades, Spielberg's films have covered many themes and genres. Spielberg's early science-fiction and adventure films were seen as archetypes of modern Hollywood blockbuster filmmaking. In later years, his films began addressing humanistic issues such as the Holocaust (in Schindler's List), the transatlantic slave trade (in Amistad), war (in Empire of the Sun, Saving Private Ryan, War Horse and Bridge of Spies) and terrorism (in Munich). His other films include Close Encounters of the Third Kind, the Indiana Jones film series, and A.I. Artificial Intelligence.
answer:

What is Spielberg's most critically acclaimed film?