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 control of associated biodiversity is one of the great agricultural challenges that farmers face. On monoculture farms, the approach is generally to eradicate associated diversity using a suite of biologically destructive pesticides, mechanized tools and transgenic engineering techniques, then to rotate crops. Although some polyculture farmers use the same techniques, they also employ integrated pest management strategies as well as strategies that are more labor-intensive, but generally less dependent on capital, biotechnology and energy.

SOLUTION: What is one of the great polyculture challenges that farmers face?

PROBLEM: Passage: A fine tribute to the fall of Warsaw and history of Poland can be found in the Warsaw Uprising Museum and in the Katyń Museum which preserves the memory of the crime. The Warsaw Uprising Museum also operates a rare preserved and operating historic stereoscopic theatre, the Warsaw Fotoplastikon. The Museum of Independence preserves patriotic and political objects connected with Poland's struggles for independence. Dating back to 1936 Warsaw Historical Museum contains 60 rooms which host a permanent exhibition of the history of Warsaw from its origins until today.

SOLUTION: Where can a tribute to the fall of Katyn be found?

PROBLEM: Passage: After the Rus' attack on Constantinople in 860, the Byzantine Patriarch Photius sent missionaries north to convert the Rus' and the Slavs. Prince Rastislav of Moravia had requested the Emperor to provide teachers to interpret the holy scriptures, so in 863 the brothers Cyril and Methodius were sent as missionaries, due to their knowledge of the Slavonic language. The Slavs had no written language, so the brothers devised the Glagolitic alphabet, later developed into Cyrillic, and standardized the language of the Slavs, later known as Old Church Slavonic. They translated portions of the Bible and drafted the first Slavic civil code and other documents, and the language and texts spread throughout Slavic territories, including Kievan Rus’. The mission of Cyril and Methodius served both evangelical and diplomatic purposes, spreading Byzantine cultural influence in support of imperial foreign policy. In 867 the Patriarch announced that the Rus' had accepted a bishop, and in 874 he speaks of an "Archbishop of the Rus'."

SOLUTION:
Who sent missionaries south?