Problem: History of India:

In 530 BC Cyrus the Great, King of the Persian Achaemenid Empire crossed the Hindu-Kush mountains to seek tribute from the tribes of Kamboja, Gandhara and the trans-India region (modern Afghanistan and Pakistan). By 520 BC, during the reign of Darius I of Persia, much of the northwestern subcontinent (present-day eastern Afghanistan and Pakistan) came under the rule of the Persian Achaemenid Empire, as part of the far easternmost territories. The area remained under Persian control for two centuries. During this time India supplied mercenaries to the Persian army then fighting in Greece.

What king ruled Persia in 520 BC?
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A: Darius I of Persia

Problem: Mainstream AC itself has evolved in a similar fashion over the years; traditional AC artists like Barbra Streisand, the Carpenters, Dionne Warwick, Barry Manilow, John Denver, and Olivia Newton-John found it harder to have major Top 40 hits as the 1980s wore on, and due to the influence of MTV, artists who were staples of the Contemporary Hit Radio format, such as Richard Marx, Michael Jackson, Bonnie Tyler, George Michael, Phil Collins, and Laura Branigan began crossing over to the AC charts with greater frequency. Collins has been described by AllMusic as "one of the most successful pop and adult contemporary singers of the '80s and beyond". However, with the combination of MTV and AC radio, adult contemporary appeared harder to define as a genre, with established soft-rock artists of the past still charting pop hits and receiving airplay alongside mainstream radio fare from newer artists at the time.
Along with Richard Marx, Bonnie Tyler, George Michael, Phil Collins, and Laura Branigan, what artist was also frequently played on Contemporary Hit Radio stations?
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Answer: Michael Jackson

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Chicago Mayor Richard M. Daley proclaimed August 10, 2005 to be "House Unity Day" in Chicago, in celebration of the "21st anniversary of house music" (actually the 21st anniversary of the founding of Trax Records, an independent Chicago-based house label). The proclamation recognized Chicago as the original home of house music and that the music's original creators "were inspired by the love of their city, with the dream that someday their music would spread a message of peace and unity throughout the world". DJs such as Frankie Knuckles, Marshall Jefferson, Paul Johnson and Mickey Oliver celebrated the proclamation at the Summer Dance Series, an event organized by Chicago's Department of Cultural Affairs.
In 2005, what anniversary was Oliver music celebrating?
A: unanswerable

Context and question: The Second Sino-Japanese War was soon followed by the resumed Chinese Civil War, and the cities of East China fell to the Communists one after another, the Kuomintang government again tried to make Sichuan its stronghold on the mainland, although it already saw some Communist activity since it was one area on the road of the Long March. Chiang Kai-Shek himself flew to Chongqing from Taiwan in November 1949 to lead the defense. But the same month Chongqing fell to the Communists, followed by Chengdu on 10 December. The Kuomintang general Wang Sheng wanted to stay behind with his troops to continue anticommunist guerilla war in Sichuan, but was recalled to Taiwan. Many of his soldiers made their way there as well, via Burma.
What other city fell following the fall of Chendu?
Answer: unanswerable

Question: Historically, migration has been recorded as much as 3,000 years ago by Ancient Greek authors including Homer and Aristotle, and in the Book of Job, for species such as storks, turtle doves, and swallows. More recently, Johannes Leche began recording dates of arrivals of spring migrants in Finland in 1749, and scientific studies have used techniques including bird ringing and satellite tracking. Threats to migratory birds have grown with habitat destruction especially of stopover and wintering sites, as well as structures such as power lines and wind farms.
Is there an answer to this question: When was migration first recorded?

Answer: 3,000 years ago

Problem: Gregorian calendar:

In conjunction with the system of months there is a system of weeks. A physical or electronic calendar provides conversion from a given date to the weekday, and shows multiple dates for a given weekday and month. Calculating the day of the week is not very simple, because of the irregularities in the Gregorian system. When the Gregorian calendar was adopted by each country, the weekly cycle continued uninterrupted. For example, in the case of the few countries that adopted the reformed calendar on the date proposed by Gregory XIII for the calendar's adoption, Friday, 15 October 1582, the preceding date was Thursday, 4 October 1582 (Julian calendar).

Why is calculating the days of the Gregorian calendar not simple?
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A:
irregularities