Final answer:
The rivalries of Philip and Richard caused a lack of unity and strategic disagreements among the Crusaders, contributing to the failure of the Third Crusade. The correct option is A.
Step-by-step explanation:
The rivalries between Philip Augustus of France and Richard the Lionheart of England greatly contributed to the failure of the Third Crusade. This lack of unity, marked by strategic disagreements and personal ambitions, undermined the crusaders' overall effectiveness.
Their inability to work together compromised the stability and coherence of the crusading forces, leading to missed opportunities and an eventual lack of significant achievement.
While the crusades were already challenged by logistics and complex geopolitical factors, these internal conflicts exacerbated the situation, making a coherent strategic approach against Muslim forces difficult.
Hence, the correct answer to the question is (A) Led to lack of unity and strategic disagreements.