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]: Winter, and a deteriorating supply situation on both sides of troops and materiel, led to a halt in ground operations. Sevastopol remained invested by the allies, while the allied armies were hemmed in by the Russian army in the interior. On 14 November a storm sank thirty allied transport ships including HMS Prince which was carrying a cargo of winter clothing.:435 The storm and heavy traffic caused the road from the coast to the troops to disintegrate into a quagmire, requiring engineers to devote most of their time to its repair including quarrying stone. A tramroad was ordered. It arrived in January with a civilian engineering crew, however it was March before it was sufficiently advanced to be of any appreciable value.:439 An Electrical telegraph was also ordered, but the frozen ground delayed its installation until March, when communications from the base port of Balaklava to the British HQ was established. The Pipe-and-cable-laying plough failed because of the hard frozen soil, but even so 21 miles of cable were laid.:449
[A]: What stopped ground operations during the winter?


[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]: On 21 April, Communist forces crossed the Yangtze River. On April 23, 1949, the Communist People's Liberation Army (PLA) captured Nanjing. The KMT government retreated to Canton (Guangzhou) until October 15, Chongqing until November 25, and then Chengdu before retreating to Taiwan on December 10. By late 1949, the PLA was pursuing remnants of KMT forces southwards in southern China, and only Tibet was left. After the establishment of the People's Republic of China in October 1949, Nanjing was initially a province-level municipality, but it was soon merged into Jiangsu province and again became the provincial capital by replacing Zhenjiang which was transferred in 1928, and retains that status to this day.
[A]:
When did the Communist troops cross the Yangtze River?