The Council of Trent was not a cause of the Protestant Reformation because it was a formal Catholic reply to the Protestant reformation itself. As a way to keep its followers from moving from Catholicism to Protestantism, the Catholic Church prompted a counter-reformation, which is marked by the Council of Trent. The Protestant reformation was already gaining popularity by the time the Council of Trent became relevant, so therefore it cannot be a cause of the reformation.
Answer: B) Council of Trent