Which is the best description of the city of Constantinople at the time of the First Crusade?

Constantinople was the capital of the Byzantine Empire, a Christian empire, when the First Crusade began. Crusader armies gathered and passed through the city on their way toward Jerusalem, so D, “a Christian city from which the Crusaders marched on Jerusalem,” is the best description. The pope lived in Rome, not Constantinople, and the city was not Muslim or neutral.

AI-written and checked against the verified answer.