Problem: Umayyad Caliphate:

The Umayyad Caliphate (Arabic: الخلافة الأموية‎, trans. Al-Khilāfat al-ʾumawiyya) was the second of the four major Islamic caliphates established after the death of Muhammad. This caliphate was centered on the Umayyad dynasty (Arabic: الأمويون‎, al-ʾUmawiyyūn, or بنو أمية, Banū ʾUmayya, "Sons of Umayya"), hailing from Mecca. The Umayyad family had first come to power under the third caliph, Uthman ibn Affan (r. 644–656), but the Umayyad regime was founded by Muawiya ibn Abi Sufyan, long-time governor of Syria, after the end of the First Muslim Civil War in 661 CE/41 AH. Syria remained the Umayyads' main power base thereafter, and Damascus was their capital. The Umayyads continued the Muslim conquests, incorporating the Caucasus, Transoxiana, Sindh, the Maghreb and the Iberian Peninsula (Al-Andalus) into the Muslim world. At its greatest extent, the Umayyad Caliphate covered 15 million km2 (5.79 million square miles), making it the largest empire (in terms of area - not in terms of population) the world had yet seen, and the fifth largest ever to exist.

How many million square miles was the Umayyad caliphate at its largest size?
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A: 5.79


Problem: Nanjing:

A monument to the huge human cost of some of the gigantic construction projects of the early Ming dynasty is the Yangshan Quarry (located some 15–20 km (9–12 mi) east of the walled city and Ming Xiaoling mausoleum), where a gigantic stele, cut on the orders of the Yongle Emperor, lies abandoned, just as it was left 600 years ago when it was understood it was impossible to move or complete it.

How long ago was the stele abandoned?
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A: 600 years ago


Problem: 2008 Sichuan earthquake:

(The Ms 6.1 earthquake on August 30, 2008 in southern Sichuan was not part of this series because it was caused by a different fault. See 2008 Panzhihua earthquake for details.)

What earthquake happened in southern Sichuan?
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A: Panzhihua earthquake


Problem: Compact disc:

Compact Disc (CD) is a digital optical disc data storage format. The format was originally developed to store and play only sound recordings but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. Audio CDs and audio CD players have been commercially available since October 1982.

What does CD stand for?
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A:
Compact Disc