Answer: a.Lending money and charging interest went against a teaching of the Catholic Church and was seen as sinful.
Explanation:
Even during the Middle Ages, Jews were a marginalized ethnic group in Europe. They were forced to do many jobs that no one else wanted. One of those jobs is banking. This work in itself implies interest, so the church considered this work a sin. So the Jews did those jobs. Jews also collected taxes in many places. Such prejudices created many prejudices against Jews.