Final answer:
The invention of the printing press and the controversy over the sale of indulgences were key factors that supported the cause of the Protestant Reformation. The correct option is - 1) The invention of the printing press.
Step-by-step explanation:
The factors that truly helped the cause of the Protestant Reformation include the invention of the printing press and the sale of indulgences. The printing press, developed by Johannes Gutenberg, was significant in spreading the ideas of reformers like Martin Luther by making literature more accessible to the public. Luther's translation of the Bible into the vernacular allowed common people to interpret the scriptures for themselves without relying solely on the Church.
On the other hand, the sale of indulgences, which was the practice where the church claimed that one could buy forgiveness from sins, caused widespread dissatisfaction that fueled the Reformation spearheaded by Martin Luther with his Ninety-five Theses. The invention of the printing press empowered the spread of these ideas, making it a cornerstone of Reformation history.