Teacher: 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.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Passage: In 1763, Spain traded Florida to the Kingdom of Great Britain for control of Havana, Cuba, which had been captured by the British during the Seven Years' War. It was part of a large expansion of British territory following the country's victory in the Seven Years' War. Almost the entire Spanish population left, taking along most of the remaining indigenous population to Cuba. The British soon constructed the King's Road connecting St. Augustine to Georgia. The road crossed the St. Johns River at a narrow point, which the Seminole called Wacca Pilatka and the British named "Cow Ford", both names ostensibly reflecting the fact that cattle were brought across the river there.
Solution: Who owned Cuba after the Eight Years War?
Reason: This question appears to be relevant to the passage as both involves words such as 'Cuba' and 'War' which also exist in the passage. The passage mentions that "after the war, almost the entire Spanish population left, taking along most of the remaining indigenous population to Cuba". This information is not sufficient to conclude that which country owned cuba.

Now, solve this instance: Passage: A new Digimon series was announced 30 months after the end of Digimon Fusion at a 15th anniversary concert and theater event for the franchise in August 2014. The series announced the return of the protagonists from the original Digimon Adventure series, most of them now as high school students. A countdown clicking game was posted on the show's official website, offering news when specific clicks were met. On December 13, 2014 the series title and a key visual featuring character designs by Atsuya Uki were revealed with Keitaro Motonaga announced as director with a tentative premiere date of Spring, 2015. However, on May 6, 2015, it was announced that tri. would not be a television series, but rather a 6-part theatrical film series. The films are being streamed in episodic format outside Japan by Crunchyroll and Hulu from the same day they premiere on Japanese theaters.
Student:
When was it announced a tri would be a television series?