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: The Crusades brought a shift in European trade routes that accelerated the decline of Kievan Rus'. In 1204 the forces of the Fourth Crusade sacked Constantinople, making the Dnieper trade route marginal. At the same time the Teutonic Knights (of the Northern Crusades) were conquering the Baltic region and threatening the Lands of Novgorod. Concurrently with it the Ruthenian Federation of Kievan Rus' started to disintegrate into smaller principalities as the Rurik dynasty grew. The local Orthodox Christianity of Kievan Rus', while struggling to establish itself in the predominantly pagan state and losing its main base in Constantinople was on the brink of extinction. Some of the main regional centres that developed later were Novgorod, Chernigov, Galich, Kiev, Ryazan, Vladimir-upon-Klyazma, Vladimir of Volyn and Polotsk.
What helped restore the Kievam Rus?