Final answer:
The Byzantine Empire sought aid from the Christian West due to threats from external invaders, notably the expansion of Seljuk and Ottoman Turks, which weakened the empire's economic and territorial stability.
Step-by-step explanation:
The Byzantine Empire sought aid from the Christian West primarily due to c) Threats from external invaders. The empire faced significant challenges that weakened its power, including ineffective rulers, loss of overseas territories, and the rise of Islamic and Italian naval dominance in the Mediterranean. Additionally, after the empire regained Constantinople, it contended with the expansion of Seljuk and then Ottoman Turks, along with other invaders, compromising its territorial integrity and leading to economic decline. These conditions, combined with the weakening of diplomatic alliances and the ambition of the nearby powers who sought to claim parts of its territory, impelled them to seek assistance from the Christian West. Despite the aim for military support to counter these threats, the call for aid inadvertently contributed to sparking the Italian Renaissance through the exchange of scholars and texts, though this cultural benefit did not prevent the ultimate fall of Constantinople to the Ottoman Turks in 1453