Before Sultan Mehmed II Conquered Constantinople in 1453, What Humiliation

Before Sultan Mehmed II conquered Constantinople in 1453, what humiliation had already been suffered by the Byzantine empire?

A) The Byzantines were forced to sell the formula for Greek Fire, a deadly weapon.
B) The previous Byzantine emperor had negotiated a union of the Eastern Orthodox Church with the Latin Church in hopes of garnishing support.
C) The Byzantines were already paying enormous tribute to the sultan.
D) In 1452 Jerusalem was seized by Muslim forces.
E) German knights had assumed control over Greece and other lands previously held by the Byzantines in Europe.