Later crusades failed for all of the following reasons except
a.
the crusaders were outnumbered
c.
the desert climate was a challenge
b.
people began to lose faith
d.
there were arguments among christian leaders

b.  people began to lose faith

Explanation:

The Crusades were a series of military campaigns in the Holy Land driven by the Pope and carried out by European Christendom between the end of the 11th century and the end of the 13th century. The main reasons for these military campaigns were religious, and the faith that took lords, peasants, and religious military orders to the Middle East did not fade away with the pass of the centuries during the Middle Ages.

In fact, after the initial victories for which European Christians took Jerusalem, Crusaders slowly started to be outnumbered by organized Muslim armies, like Saladin's army at the end of the 12th century, and later by the Mameluke and Mongol armies.

The desert was also a big challenge for crusaders, who carried heavy armors and did not know the terrain as well as the local enemies.

One final problem was that there was no consensus among the Christian leaders. The Pope and the religious military orders wanted to recover Jerusalem, but many kings and lords in Europe saw it as a waste of energy and resources since most of them were focused on local problems. The kings, indeed, were on a race to gain power and control over territory, and many of them, like Philip IV from France, saw the Pope as a political rival.

St. Lawrence River

I think. Sorry if I'm wrong <3