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.

[Q]: Passage: The oak forests of the southern and central Appalachians consist largely of black, northern red, white, chestnut and scarlet oaks (Quercus velutina, Q. rubra, Q. alba, Q. prinus and Q. coccinea) and hickories, such as the pignut (Carya glabra) in particular. The richest forests, which grade into mesic types, usually in coves and on gentle slopes, have dominantly white and northern red oaks, while the driest sites are dominated by chestnut oak, or sometimes by scarlet or northern red oaks. In the northern Appalachians the oaks, except for white and northern red, drop out, while the latter extends farthest north.
[A]: What is the dominate type of oak in the Appalachians?


[Q]: Passage: The war had removed Bermuda's primary trading partners, the American colonies, from the empire, and dealt a harsh blow to Bermuda's merchant shipping trade. This also suffered due to the deforestation of Bermuda, as well as the advent of metal ships and steam propulsion, for which it did not have raw materials. During the course of the following War of 1812, the primary market for Bermuda's salt disappeared as the Americans developed their own sources. Control of the Turks had passed to the Bahamas in 1819.
[A]: What was the primary market for Bermuda following the War of 1812?


[Q]: Passage: However, by the turn of the 1990s the downward trend was starting to reverse; England had been successful in the 1990 FIFA World Cup, reaching the semi-finals. UEFA, European football's governing body, lifted the five-year ban on English clubs playing in European competitions in 1990 (resulting in Manchester United lifting the UEFA Cup Winners' Cup in 1991) and the Taylor Report on stadium safety standards, which proposed expensive upgrades to create all-seater stadiums in the aftermath of the Hillsborough disaster, was published in January of that year.
[A]:
By the turn of which decade was the upward trend beginning to reverse?