instruction:
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.
question:
Passage: The logical format of an audio CD (officially Compact Disc Digital Audio or CD-DA) is described in a document produced in 1980 by the format's joint creators, Sony and Philips. The document is known colloquially as the Red Book CD-DA after the colour of its cover. The format is a two-channel 16-bit PCM encoding at a 44.1 kHz sampling rate per channel. Four-channel sound was to be an allowable option within the Red Book format, but has never been implemented. Monaural audio has no existing standard on a Red Book CD; thus, mono source material is usually presented as two identical channels in a standard Red Book stereo track (i.e., mirrored mono); an MP3 CD, however, can have audio file formats with mono sound.
answer:
What was the sampling rate for the four-channel sound?


question:
Passage: Menander Protector mentions a Daurentius (577–579) that slew an Avar envoy of Khagan Bayan I. The Avars asked the Slavs to accept the suzerainty of the Avars, he however declined and is reported as saying: "Others do not conquer our land, we conquer theirs – so it shall always be for us".
answer:
When did Protector live?


question:
Passage: The "Mittelschule" is a school in some States of Germany that offers regular classes and remedial classes but no college preparatory classes. In some States of Germany, the Hauptschule does not exist, and any student who has not been accepted by another school has to attend the Mittelschule. Students may be awarded the Hauptschulabschluss or the Mittlere Reife but not the Abitur.
answer:

What kind of classes are offered in Mittelschule?