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.

[EX Q]: Passage: Even though some proofs of complexity-theoretic theorems regularly assume some concrete choice of input encoding, one tries to keep the discussion abstract enough to be independent of the choice of encoding. This can be achieved by ensuring that different representations can be transformed into each other efficiently.
[EX A]: What can not be achieved by ensuring different representations can transformed into each other efficiently?

[EX Q]: Passage: Some Samoans are spiritual and religious, and have subtly adapted the dominant religion of Christianity to 'fit in' with fa'a Samoa and vice versa. As such, ancient beliefs continue to co-exist side-by-side with Christianity, particularly in regard to the traditional customs and rituals of fa'a Samoa. The Samoan culture is centred around the principle of vāfealoa'i, the relationships between people. These relationships are based on respect, or fa'aaloalo. When Christianity was introduced in Samoa, most Samoan people converted. Currently 98% of the population identify themselves as Christian.
[EX A]: What religion is practiced by the fa'aaloalo?

[EX Q]: Passage: At extremely large airports, a circuit is in place but not usually used. Rather, aircraft (usually only commercial with long routes) request approach clearance while they are still hours away from the airport, often before they even take off from their departure point. Large airports have a frequency called Clearance Delivery which is used by departing aircraft specifically for this purpose. This then allows aircraft to take the most direct approach path to the runway and land without worrying about interference from other aircraft. While this system keeps the airspace free and is simpler for pilots, it requires detailed knowledge of how aircraft are planning to use the airport ahead of time and is therefore only possible with large commercial airliners on pre-scheduled flights. The system has recently become so advanced that controllers can predict whether an aircraft will be delayed on landing before it even takes off; that aircraft can then be delayed on the ground, rather than wasting expensive fuel waiting in the air.
[EX A]:
What do aircraft use instead of requesting approach clearance at very large airports?