one who believes in atonement
Option B.
Step-by-step explanation:
Crusaders were the people who wanted to bring about a change in the fields and areas of religion, political change and social change. They wanted to participate in the crusade for atoning for their sins and the wrong done by them.
Thus these were the people who believed in atonement, they believed that they could make up, do reparation for the wrong done by participating in the war of crusades.