Which of the following practices was not a source of contention between the catholic church and martin luther?
1. the practice of purchasing religious positions
2. the concept of papal infallibility
3. the sacrament of communion
4. the sale of indulgences

The practice of the sacrament comunion was not a source of contention between the Catholic Church and Martin Luther. Option 3 is correct.

Martin Luther did not believe in transubstantiation, he believed in consubstantiation.

Holy Communion also refered to as Eucharist is a Christian rite that is regarded a sacrament in most churches, and as an ordinance in others. According to the New Testament, the rite was instituted by Jesus Christ during the Last Supper; giving his disciples bread and wine during the Passover meal, Jesus commanded his followers to "do this in memory of me" while referring to the bread as "my body" and the cup of wine as "the new covenant in my blood."

i think the answer is b.