The correct answer are:
A.) to eliminate corruption from the Catholic Church
C.) to keep Catholics from converting to Protestantism
The Counter-Reform was the move made by the Catholic Church in order to avoid the expansion of the Protestant Reform of the 16th century, which had weakened the power of the Church. The Protestant Reform started with the religious movement led by Martin Luther who opposed to the corruption and elitism of the Catholic Church. Many princes and kings from Europe joined his movement and other Protestant branches started to appear in different regions, challenging the dominant position of the Roman Church.
The Counter-Reform was the answer to eliminate the corruption within the Catholic institution and, at the same time, to keep Catholics from converting to Protestantism. The methods delivered by the Church in doing so included new religious orders, like the Jesuits, religious wars, and the creation of the Holy Inquisition.