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: In manufacturing the glass bulb, a type of "ribbon machine" is used. A continuous ribbon of glass is passed along a conveyor belt, heated in a furnace, and then blown by precisely aligned air nozzles through holes in the conveyor belt into molds. Thus the glass bulbs are created. After the bulbs are blown, and cooled, they are cut off the ribbon machine; a typical machine of this sort produces 50,000 bulbs per hour. The filament and its supports are assembled on a glass stem, which is fused to the bulb. The air is pumped out of the bulb, and the evacuation tube in the stem press is sealed by a flame. The bulb is then inserted into the lamp base, and the whole assembly tested.

SOLUTION: What type of machine is not used in manufacturing light bulbs?

PROBLEM: Passage: The use of animal fur in clothing dates to prehistoric times. It is currently associated in developed countries with expensive, designer clothing, although fur is still used by indigenous people in arctic zones and higher elevations for its warmth and protection. Once uncontroversial, it has recently been the focus of campaigns on the grounds that campaigners consider it cruel and unnecessary. PETA, along with other animal rights and animal liberation groups have called attention to fur farming and other practices they consider cruel.

SOLUTION: What has not been used for clothing since prehistoric times?

PROBLEM: Passage: The tallest building in Downtown Jacksonville's skyline is the Bank of America Tower, constructed in 1990 as the Barnett Center. It has a height of 617 ft (188 m) and includes 42 floors. Other notable structures include the 37-story Wells Fargo Center (with its distinctive flared base making it the defining building in the Jacksonville skyline), originally built in 1972-74 by the Independent Life and Accident Insurance Company, and the 28 floor Riverplace Tower which, when completed in 1967, was the tallest precast, post-tensioned concrete structure in the world.

SOLUTION:
In the shortest building in downtown Jacksonville?