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.

Passage: Iron is usually found as iron ore on Earth, except for one deposit of native iron in Greenland, which was used by the Inuit people. Native copper, however, was found worldwide, along with silver, gold and platinum, which were also used to make tools, jewelry, and other objects since Neolithic times. Copper was the hardest of these metals, and the most widely distributed. It became one of the most important metals to the ancients. Eventually, humans learned to smelt metals such as copper and tin from ore, and, around 2500 BC, began alloying the two metals to form bronze, which is much harder than its ingredients. Tin was rare, however, being found mostly in Great Britain. In the Middle East, people began alloying copper with zinc to form brass. Ancient civilizations took into account the mixture and the various properties it produced, such as hardness, toughness and melting point, under various conditions of temperature and work hardening, developing much of the information contained in modern alloy phase diagrams. Arrowheads from the Chinese Qin dynasty (around 200 BC) were often constructed with a hard bronze-head, but a softer bronze-tang, combining the alloys to prevent both dulling and breaking during use.
What is usually found his iron ore in Greenland?

Passage: Of Alaska's 2010 Census population figure of 710,231, 20,429 people, or 2.88% of the population, did not live in an incorporated city or census-designated place. Approximately three-quarters of that figure were people who live in urban and suburban neighborhoods on the outskirts of the city limits of Ketchikan, Kodiak, Palmer and Wasilla. CDPs have not been established for these areas by the United States Census Bureau, except that seven CDPs were established for the Ketchikan-area neighborhoods in the 1980 Census (Clover Pass, Herring Cove, Ketchikan East, Mountain Point, North Tongass Highway, Pennock Island and Saxman East), but have not been used since. The remaining population was scattered throughout Alaska, both within organized boroughs and in the Unorganized Borough, in largely remote areas.
In 2010, what percent of Alaska's population did not live in a city or CPD?

Passage: During the 20th century, historians John Gallagher (1919–1980) and Ronald Robinson (1920–1999) constructed a framework for understanding European imperialism. They claim that European imperialism was influential, and Europeans rejected the notion that "imperialism" required formal, legal control by one government over another country. "In their view, historians have been mesmerized by formal empire and maps of the world with regions colored red. The bulk of British emigration, trade, and capital went to areas outside the formal British Empire. Key to their thinking is the idea of empire 'informally if possible and formally if necessary.'"[attribution needed] Because of the resources made available by imperialism, the world's economy grew significantly and became much more interconnected in the decades before World War I, making the many imperial powers rich and prosperous.

Which historian was popular in the 21st century?