It is hard to know for certain which country to give as the answer for this question as we do not have a list from which to choose. There were many countries, and not just one country, that remained predominantly Roman Catholic even after the Protestant Reformation.
The Protestant Reformation got its start in what is now Germany. It is usually said to have started when Martin Luther published his 95 Theses in which he criticized various aspects of Catholic belief and practice. Perhaps because it started in Germany, it had its greatest impact in that area. Many parts of Germany and neighboring countries like Switzerland became heavily Protestant. England and Scotland became Protestant as well. However, most of the rest of Western Europe remained predominantly Catholic. Italy (which, like Germany, was not yet a united country) remained Catholic. So did Spain, Portugal, most of France, and Ireland. I suggest that you look at your list and see which of these countries is mentioned there. These are the countries of Western Europe that remained Catholic after the Reformation.
Please follow the links below for maps showing religious affiliation in Europe after the Reformation.