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.

[EX 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]
[EX A]: What time cycle did studies in 1938 and 1990s use on humans?

[EX Q]: Up to the 1990s, the Federal District was the most populous federal entity in Mexico, but since then its population has remained stable at around 8.7 million. The growth of the city has extended beyond the limits of the Federal District to 59 municipalities of the state of Mexico and 1 in the state of Hidalgo. With a population of approximately 19.8 million inhabitants (2008), it is one of the most populous conurbations in the world. Nonetheless, the annual rate of growth of the Metropolitan Area of Mexico City is much lower than that of other large urban agglomerations in Mexico, a phenomenon most likely attributable to the environmental policy of decentralization. The net migration rate of the Federal District from 1995 to 2000 was negative.
[EX A]: How many people live in the Federal District? 

[EX Q]: At times a character may "turn", altering their face/heel alignment. This may be an abrupt, surprising event, or it may slowly build up over time. It almost always is accomplished with a markable change in behavior on the part of the character. Some turns become defining points in a wrestler's career, as was the case when Hulk Hogan turned heel after being a top face for over a decade. Others may have no noticeable effect on the character's status. If a character repeatedly switches between being a face and heel, this lessens the effect of such turns, and may result in apathy from the audience. Vince McMahon is a good example of having more heel and face turns than anyone in WWE history.
[EX A]:
What might a character do with their persona?