Final answer:
The development of the concepts of purgatory and Mary's sinlessness is associated with the Counter-Reformation period, which was a Catholic resurgence to address challenges posed by the Protestant Reformation.
Step-by-step explanation:
The concepts of purgatory and Mary's sinlessness developed during the period of the Counter-Reformation. This period was marked by a Catholic resurgence in response to the Protestant Reformation, beginning with the Council of Trent in 1545 and ending after the Thirty Years' War in 1648. The Counter-Reformation was characterized by efforts to reform the church internally, reaffirming traditional Catholic doctrines - such as Mary's Immaculate Conception and the existence of purgatory - and to counter the growth of Protestantism.