You can talk about the boarder crisis along the Estonian boarder and Russian boarder. The is called a crisis because there is a tradition steeped kingdom called the Seto caught directly in the middle of it(their kingdom is split half and half).
When Alexius I Komnenoi implored the pope (Urban II) for help, he meant it to reconquer the lost Byzantine lands (and therefore return in to their de facto ruler, a.k.a., the Byzantines). Urban however, decided to merely use that as a façade in order to then invade the Muslims, and retake the holy land.
He also saw the wanted to unite Christianity as a whole (All the sects at the time, Orthodoxy, Catholicism, Paulicianism, Iconoclasts, etc. into a single conglomerate, fighting a common enemy.)
The Igbo lacked a centralized political organization.
Hope this helps:)
I believe the answer is: B.because of advances in science, medicine, technology, and the arts
During the hand civilization, China developed many advancement in use of herbs for medicinal purpose and adopted many technology from all across the world which increase their agricultural production capacity.
Their artworks were also developed to the point where it became a hot commodity among European nobles.
