Which of the following was a major reason for the weakening of the Byzantine Empire?

The weakening of the Byzantine Empire can be attributed significantly to continuous invasions and internal strife. Throughout its history, the empire faced numerous external threats, including invasions from various groups such as the Seljuk Turks and later the Ottoman Turks. These invasions placed immense pressure on the empire's borders, draining resources and weakening its military capabilities.

In addition to external invasions, internal strife, such as political corruption, social unrest, and power struggles, further destabilized the state. This internal discord made it difficult for the empire to present a unified defense or effectively respond to external threats. The combination of these factors created a situation where the Byzantine Empire struggled to maintain its integrity and power, ultimately leading to its decline.

Economic prosperity, strong military alliances, and the expansion of trade networks generally indicate strengths rather than weaknesses. While these factors might have been present at certain times, they did not serve to bolster the empire in the long term against the overwhelming challenges posed by invasions and internal disunity.