The most accurate response regarding the connection between the growth of the Spanish Empire and the spread of Catholicism is:
After Spain merged the kingdoms of Aragon and Castile, it acquired Granada and was able to use it as a launching point to spread Christianity to the Americas.
This reflects the historical context in which the unification of Spain under the Catholic Monarchs (Isabella I of Castile and Ferdinand II of Aragon) facilitated both territorial expansion and the promotion of Catholicism, particularly following the Reconquista and the subsequent voyages of exploration to the New World. Granada, the last Muslim stronghold in Spain, was captured in 1492, which effectively solidified Catholic rule and provided the impetus for overseas missionary efforts.