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]: The primary physiological cue for migration are the changes in the day length. These changes are also related to hormonal changes in the birds. In the period before migration, many birds display higher activity or Zugunruhe (German: migratory restlessness), first described by Johann Friedrich Naumann in 1795, as well as physiological changes such as increased fat deposition. The occurrence of Zugunruhe even in cage-raised birds with no environmental cues (e.g. shortening of day and falling temperature) has pointed to the role of circannual endogenous programs in controlling bird migrations. Caged birds display a preferential flight direction that corresponds with the migratory direction they would take in nature, changing their preferential direction at roughly the same time their wild conspecifics change course.
[EX A]: What is the primary cue for migration?

[EX Q]: Electricity in the Richmond Metro area is provided by Dominion Virginia Power. The company, based in Richmond, is one of the nation's largest producers of energy, serving retail energy customers in nine states. Electricity is provided in the Richmond area primarily by the North Anna Nuclear Generating Station and Surry Nuclear Generating Station, as well as a coal-fired station in Chester, Virginia. These three plants provide a total of 4,453 megawatts of power. Several other natural gas plants provide extra power during times of peak demand. These include facilities in Chester, and Surry, and two plants in Richmond (Gravel Neck and Darbytown).
[EX A]: Who is Richmond's electricity supplier?

[EX 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.
[EX A]:
When did the Communist troops cross the Yangtze River?