TASK DEFINITION: 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.
PROBLEM: Passage: The use of alloys by humans started with the use of meteoric iron, a naturally occurring alloy of nickel and iron. It is the main constituent of iron meteorites which occasionally fall down on Earth from outer space. As no metallurgic processes were used to separate iron from nickel, the alloy was used as it was. Meteoric iron could be forged from a red heat to make objects such as tools, weapons, and nails. In many cultures it was shaped by cold hammering into knives and arrowheads. They were often used as anvils. Meteoric iron was very rare and valuable, and difficult for ancient people to work.

SOLUTION: What was the first man-made alloy used by humans?

PROBLEM: Passage: The most-commonly accepted theory is that these events were triggered by the onset of an ice age, in the Hirnantian faunal stage that ended the long, stable greenhouse conditions typical of the Ordovician. The ice age was probably not as long-lasting as once thought; study of oxygen isotopes in fossil brachiopods shows that it was probably no longer than 0.5 to 1.5 million years. The event was preceded by a fall in atmospheric carbon dioxide (from 7000ppm to 4400ppm) which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it. Evidence of these ice caps have been detected in Upper Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time.

SOLUTION: What faunel stage triggered the greenhouse conditions of the Ordovician?

PROBLEM: Passage: Utrecht is the centre of a densely populated area, which makes concise definitions of its agglomeration difficult, and somewhat arbitrary. The smaller Utrecht agglomeration of continuously built up areas counts some 420,000 inhabitants and includes Nieuwegein, IJsselstein and Maarssen. It is sometimes argued that the close by municipalities De Bilt, Zeist, Houten, Vianen, Driebergen-Rijsenburg (Utrechtse Heuvelrug), and Bunnik should also be counted towards the Utrecht agglomeration, bringing the total to 640,000 inhabitants. The larger region, including slightly more remote towns such as Woerden and Amersfoort counts up to 820,000 inhabitants.

SOLUTION:
What is the population of the original bishopric?