Problem: Early Muslim armies stayed in encampments away from cities because Umar feared that they might get attracted to wealth and luxury. In the process, they might turn away from the worship of God and start accumulating wealth and establishing dynasties. When Uthman ibn al-Affan became very old, Marwan I, a relative of Muawiyah I, slipped into the vacuum, became his secretary, slowly assumed more control and relaxed some of these restrictions. Marwan I had previously been excluded from positions of responsibility. In 656, Muhammad ibn Abi Bakr, the son of Abu Bakr, the adopted son of Ali ibn Abi Talib, and the great grandfather of Ja'far al-Sadiq, showed some Egyptians the house of Uthman ibn al-Affan. Later the Egyptians ended up killing Uthman ibn al-Affan.
Who was the great grandson of Muhammad ibn Ali Bakr?
The answer is the following: Ja'far al-Sadiq

Problem: On the Origin of Species was first published on Thursday 24 November 1859, priced at fifteen shillings with a first printing of 1250 copies. The book had been offered to booksellers at Murray's autumn sale on Tuesday 22 November, and all available copies had been taken up immediately. In total, 1,250 copies were printed but after deducting presentation and review copies, and five for Stationers' Hall copyright, around 1,170 copies were available for sale. Significantly, 500 were taken by Mudie's Library, ensuring that the book promptly reached a large number of subscribers to the library. The second edition of 3,000 copies was quickly brought out on 7 January 1860, and incorporated numerous corrections as well as a response to religious objections by the addition of a new epigraph on page ii, a quotation from Charles Kingsley, and the phrase "by the Creator" added to the closing sentence. During Darwin's lifetime the book went through six editions, with cumulative changes and revisions to deal with counter-arguments raised. The third edition came out in 1861, with a number of sentences rewritten or added and an introductory appendix, An Historical Sketch of the Recent Progress of Opinion on the Origin of Species, while the fourth in 1866 had further revisions. The fifth edition, published on 10 February 1869, incorporated more changes and for the first time included the phrase "survival of the fittest", which had been coined by the philosopher Herbert Spencer in his Principles of Biology (1864).
Which institution bought 500 copies of the book, ensuring that a large number of people would have access to it?
The answer is the following: Mudie's Library

Problem: The Slavic autonym *Slovenin is usually considered (e.g. by Roman Jakobson) a derivation from slovo "word", originally denoting "people who speak (the same language)," i.e. people who understand each other, in contrast to the Slavic word denoting "foreign people" nemci, meaning "mumbling, murmuring people" (from Slavic *nem "mumbling, mute").
What slavic word denotes "foreign people?"
The answer is the following: nemci

Problem: The Hashimiyya movement (a sub-sect of the Kaysanites Shia), led by the Abbasid family, overthrew the Umayyad caliphate. The Abbasids were members of the Hashim clan, rivals of the Umayyads, but the word "Hashimiyya" seems to refer specifically to Abu Hashim, a grandson of Ali and son of Muhammad ibn al-Hanafiyya. According to certain traditions, Abu Hashim died in 717 in Humeima in the house of Muhammad ibn Ali, the head of the Abbasid family, and before dying named Muhammad ibn Ali as his successor. This tradition allowed the Abbasids to rally the supporters of the failed revolt of Mukhtar, who had represented themselves as the supporters of Muhammad ibn al-Hanafiyya.
Who led the Hashimiyya movement?
The answer is the following:
Abbasid family