In the Middle Ages who would have been considered a heretic by the church?

A. A European knight who did not join the crusades
B. A Christian who did not follow excepted church teachings.
C. Who fought against Christian Crusaders in Jerusalem
D. A Jew, who refused to convert to Christianity.

All of the above options could have been considered heretics by the church in the Middle Ages, depending on the specific circumstances and the views of the church authorities at that time.