Answer:
D.Naturalization
Explanation:
U.S. Citizenship can be taken through the process of Naturalization. Naturalization is a process in which a non-U.S. citizen can becomes a U.S. citizen through a process and they are entitled to its protection, can authorise their citizenship to the United States and are able to exercise their rights as citizens.
The legal process that allows German nationals like the Bruenhoffs to become U.S. citizens is known as Naturalization.
Hence, the correct answer is "D.Naturalization".
