A. challenges to the teachings of the Roman Catholic Church, including the sacrament of baptism
Martin Luther's 95 Theses primarily focused on the sale of indulgences and other practices of the Catholic Church, addressing issues related to salvation and church authority. While they did not specifically challenge the sacrament of baptism, they did contain general critiques of the Church's teachings and practices. Options B, C, and D are not relevant to the content of the 95 Theses.