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.

[EX Q]: Passage: Infrared reflectography (fr; it; es), as called by art conservators, can be applied to paintings to reveal underlying layers in a completely non-destructive manner, in particular the underdrawing or outline drawn by the artist as a guide. This often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting. Art conservators are looking to see whether the visible layers of paint differ from the underdrawing or layers in between such alterations are called pentimenti when made by the original artist. This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti the more likely a painting is to be the prime version. It also gives useful insights into working practices.
[EX A]: What painting technique is used to reveal working practices?

[EX Q]: Passage: The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels. Two ratios are used, the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio. These ratios have been subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance. The signal-to-noise ratio is defined as the standard deviation of a weighted average of the luminance and color of individual pixels. The noise-based speed is mostly determined by the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter.
[EX A]: Which ratio was subjectively determined?

[EX Q]: Passage: Some Huguenots settled in Bedfordshire, one of the main centres of the British lace industry at the time. Although 19th century sources have asserted that some of these refugees were lacemakers and contributed to the East Midlands lace industry, this is contentious. The only reference to immigrant lacemakers in this period is of twenty-five widows who settled in Dover, and there is no contemporary documentation to support there being Huguenot lacemakers in Bedfordshire. The implication that the style of lace known as 'Bucks Point' demonstrates a Huguenot influence, being a "combination of Mechlin patterns on Lille ground", is fallacious: what is now known as Mechlin lace did not develop until first half of the eighteenth century and lace with Mechlin patterns and Lille ground did not appear until the end of the 18th century, when it was widely copied throughout Europe.
[EX A]:
How many immigrant lacemakers were there in Bedfordshire?