Answer:
The Investiture Controversy between the Holy Roman Emperor and the pope was Option B: who could appoint church officers, the secular emperor or the pope.
Explanation:
During the Middle Ages, the 'Medieval Christian church' was led by Pope and the nation was led by the king. One great disagreement between Pope Gregory VII and King Henry IV (of Holy Roman Emperor) was the question of who would appoint the local church officials. Henry thought that he should have the right to appoint the bishops of the church as he was the king. And Pope opposed stating that he should have this power.
It was not because of how the crusades should be funded or on taxes.