For What Reason Did the Military Forces of the Christian

For what reason did the military forces of the Christian Crusaders fail to make inroads into the Islamic heartland?

A) Christian military technology was so inferior to that of the Muslim forces that the Christians were unable to capture any major cities.
B) The various Christian peoples were never able to unite in a common purpose.
C) Venice,Genoa,and Pisa refused to join the Crusades because the conflict cut into their trade with the East.
D) The capital cities of the Muslim kingdoms,such as Damascus and Baghdad,were far inland.