Well, it depends. Technically all of those answers could SHAPE culture, but language, religion, and government are the best answers. People can still practice their culture despite where they are in the world, after all. So A, B, and C.
The Spanish missions introduced a new religion, so this was one significant change, and they insisted that the Native Americans follow their religion, but also other cultural aspects ( they taught them Spanish for example). Additional change was a before their life was very unregulated and the Spanish introduced a lot of rules.
