This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

[Q]: The diversion of heavier bombers to the Balkans meant that the crews and units left behind were asked to fly two or three sorties per night. Bombers were noisy, cold, and vibrated badly. Added to the tension of the mission which exhausted and drained crews, tiredness caught up with and killed many. In one incident on 28/29 April, Peter Stahl of KG 30 was flying on his 50th mission. He fell asleep at the controls of his Ju 88 and woke up to discover the entire crew asleep. He roused them, ensured they took oxygen and Dextro-Energen tablets, then completed the mission.
[A]: How many sorties a night were crews asked to fly?


[Q]: Studies by Nathaniel Kleitman in 1938 and by Derk-Jan Dijk and Charles Czeisler in the 1990s put human subjects on enforced 28-hour sleep–wake cycles, in constant dim light and with other time cues suppressed, for over a month. Because normal people cannot entrain to a 28-hour day in dim light if at all,[citation needed] this is referred to as a forced desynchrony protocol. Sleep and wake episodes are uncoupled from the endogenous circadian period of about 24.18 hours and researchers are allowed to assess the effects of circadian phase on aspects of sleep and wakefulness including sleep latency and other functions.[page needed]
[A]: What time cycle did studies in 1938 and 1990s use on humans?


[Q]: 181st Street is served by two New York City Subway lines; there is a 181st Street station at Fort Washington Avenue on the IND Eighth Avenue Line (A trains) and a 181st Street station at St. Nicholas Avenue on the IRT Broadway – Seventh Avenue Line (1 trains). The stations are about 500 metres (550 yd) from each other and are not connected. The George Washington Bridge Bus Terminal is a couple of blocks south on Fort Washington Avenue. 181st Street is also the last south/west exit in New York on the Trans-Manhattan Expressway (I-95), just before crossing the George Washington Bridge to New Jersey.
[A]:
How many subway lines serve 181st Street?