Which response by the Roman Catholic Church to the Protestant Reformation clarified the doctrines of the church?

Answer 1

Roman Catholic AnswerThe Council of Trent was called in 1545 by the Holy Father to combat Protestantism and reform the discipline of the Church; it was longest and one of the most important of the general councils. It issued almost nothing new, it just restated the long time teaching of the Church, in some cases putting it into specific words and giving it the infallible approval of a General Council in Communion with the Holy Father. The primary document that came out of the Council was the canons and decrees, a copy of which is at that link below. As called for by the Council, the Mass was codified, and any Mass that was not at least two centuries old was abandoned. After the Council, the Holy Father promulgated a new Catechism to be used throughout the Church, a copy of which may be viewed at the second link below.

from A Catholic Dictionary, edited by Donald Attwater, Second edition, revised 1957

Trent, The council of. The 19th ecumenical council held at Trent in the Austrian Tyrol, 1545-63, summoned for the purpose of combating Protestantism and reforming the discipline of the Church; the longest and one of the most important of all general councils. It dealt in detail with the doctrinal innovations of the Reformers and with those gross abuses which gave them an opportunity to take root. It was one of the most important events of modern history and has had lasting effect. The principal dogmatic decisions were: the confirmation of the Nicene creed; the authenticity of the Latin Vulgate and the canonicity of all books contained therein and of them only; the definition of the doctrine of Original Sin; the precision of the doctrine of Justification, condemning justification by faith alone and imputation of grace; the condemnation of thirty errors about the sacraments; the definition of the Real Presence and of Transubstantiation as its mode; the precision of the doctrine of the sacraments of Penance and Extreme Unction; the declaration that holy communion in both kinds was not necessary for lay-people and clerics not celebrating, Christ being received whole and entire under either species; the precision of doctrine concerning the sacrifice of the Mass and the sacraments of holy Orders and Matrimony; the affirmation of the doctrines of Purgatory, of the invocation of saints and the veneration of them, their relics and images, and of Indulgences. Far-reaching decrees of reformation in discipline and morals were adopted involving many alterations of canon law, e.g. the decree Tamatsi. . . . Cardinal Pole, afterwards of Canterbury, was a presiding legate at the opening.