The correct answer is B) He disagreed with the selling of indulgences.
The statement that best explains why Martin Luther was dissatisfied with the Catholic Church was "He disagreed with the selling of indulgences."
That was the main reason for the differences he had with the Catholic church hierarchy.
Martin Luther was a German priest who wrote the renowned document titled "95 Theses," in which he critiqued and expressed his arguments against many practices of the Catholic church. His position derivated in the split of the church, given birth to Protestantism.