In Reformation thought, there are three marks of a true church: the right preaching of the gospel, the right administration of the sacraments, and which of the following

church discipline

church growth

church music

church youth groups

Answer: church discipline

Explanation: while there are a variety of churches serving consumer needs, in the time of the Reformation, there were a few including the Roman Catholic, Orthodox, Anabaptist, Lutheran, and Reformed churches. Presently there are even more organizations calling themselves churches, as a result, The Reformers searched the Word of God to answer the question as to which churches were actually churches and came up with the three marks of the true church which are: the right preaching of the gospel, the right administration of the sacraments, and church discipline. This was to ensure that all children of God were in churches that feed their souls with the true Word of God.

church discipline

Explanation:

In protestant theology, a true church is recognized based on three criteria, these are; whether if the church preaches the right gospel, if the church administers the holy sacrament properly and whether if the church enforces discipline on failing/backsliding members in an attempt to keep them in the right part.