Final answer:
Heretical groups responded to medieval Catholic Church problems by fostering new spiritual practices and criticizing church corruption, laying the groundwork for the Protestant Reformation.
Step-by-step explanation:
One way in which heretical groups responded to problems within the medieval Catholic Church was by developing new forms of spirituality and challenging the church's authority. Groups like the Spiritual Franciscans and the Lollards criticized the church for clerical wealth and corruption, emphasizing ascetic practices that rejected worldly goods and strict self-discipline. Their activities posed significant challenges to the ecclesiastical hierarchy and sowed the seeds of the Protestant Reformation.
Martin Luther played a crucial role in this period, critiquing the Church's greed and abuse of power, and disputing the doctrine of indulgences and papal authority. His actions led to the publication of the Ninety-five Theses, sparking the Protestant Reformation and leading to a wider religious and political upheaval in Europe. The actions of heretical groups in challenging the established order of the medieval Catholic Church reflected a burgeoning desire for religious reform and greater personal piety.