The turks were defeated by crusaders at jerusalem because
a. they were severely outnumbered.
c. they did not have horses.
b. they suffered from the heat.
d. they could not remain united

The Turks were defeated by the Crusaders at Jerusalem because they could not remain united. The correct option among all the options that have been given in the question is option "d". The Crusaders could never have defeated the Turks if the Turks remained united. This weakness was taken advantage of by the Crusaders and so the Turks did not stand a chance of winning.