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.

Example Input: Passage: In the floor, just inside the great west door, in the centre of the nave, is the tomb of The Unknown Warrior, an unidentified British soldier killed on a European battlefield during the First World War. He was buried in the abbey on 11 November 1920. This grave is the only one in the abbey on which it is forbidden to walk.[citation needed]
Example Output: When was The Known Warrior buried?

Example Input: Passage: Some alloys occur naturally, such as electrum, which is an alloy that is native to Earth, consisting of silver and gold. Meteorites are sometimes made of naturally occurring alloys of iron and nickel, but are not native to the Earth. One of the first alloys made by humans was bronze, which is made by mixing the metals tin and copper. Bronze was an extremely useful alloy to the ancients, because it is much stronger and harder than either of its components. Steel was another common alloy. However, in ancient times, it could only be created as an accidental byproduct from the heating of iron ore in fires (smelting) during the manufacture of iron. Other ancient alloys include pewter, brass and pig iron. In the modern age, steel can be created in many forms. Carbon steel can be made by varying only the carbon content, producing soft alloys like mild steel or hard alloys like spring steel. Alloy steels can be made by adding other elements, such as molybdenum, vanadium or nickel, resulting in alloys such as high-speed steel or tool steel. Small amounts of manganese are usually alloyed with most modern-steels because of its ability to remove unwanted impurities, like phosphorus, sulfur and oxygen, which can have detrimental effects on the alloy. However, most alloys were not created until the 1900s, such as various aluminium, titanium, nickel, and magnesium alloys. Some modern superalloys, such as incoloy, inconel, and hastelloy, may consist of a multitude of different components.
Example Output: What is a man-made alloy of silver and gold?

Example Input: Passage: On June 18, 2009, the National Archives announced the launching of a YouTube channel "to showcase popular archived films, inform the public about upcoming events around the country, and bring National Archives exhibits to the people." Also in 2009, the National Archives launched a Flickr photostream to share portions of its photographic holdings with the general public. A new teaching with documents website premiered in 2010 and was developed by the education team. The website features 3,000 documents, images, and recordings from the holdings of the Archives. The site also features lesson plans and tools for creating new classroom activities and lessons.
Example Output:
On what date did YouTube begin showing videos online?