The best answer to the question about the use of Salic law and Christian conversion by Germanic rulers is:
B. create cultural unity across central Europe
Salic law, which governed inheritance and property rights, and the conversion to Christianity were both tools used by Germanic rulers to unify their diverse territories and consolidate power. Christian conversion helped to establish a common religious framework, while Salic law provided a legal structure that could help integrate various tribes and factions under a single ruler, promoting cultural cohesion.