Answer:
D. a court official of the Byzantine empire living in Constantinople.
Step-by-step explanation:
The only other answer that even would make sense is A.
A is wrong though because the First Crusades captured Jerusalem that was being ruled by Muslims. The first crusades were not a failure so this automatically excluded option A and option B. Option C is eliminated by the simple fact that it doesn't make sense. Fourth Crusades were when Constantinople was attacked.