What are the two primary ways to become a natural-born U.S. citizen?

The correct answer identifies the two primary ways to acquire natural-born U.S. citizenship: being born on U.S. soil (jus soli) or being born to parents who are U.S. citizens (jus sanguinis). This aligns with the principles established in the 14th Amendment of the U.S. Constitution, which grants citizenship to anyone born in the United States, and the Immigration and Nationality Act, which extends citizenship to children born abroad to American citizens.

The concepts of naturalization and marriage to a U.S. citizen pertain to the process by which someone becomes a citizen after birth, rather than being natural-born citizens. While residency and investment are related to immigration and legal status, they do not confer natural-born citizenship. Similarly, being adopted by U.S. citizens does not qualify one as a natural-born citizen; it can lead to citizenship through a legal process, but not through birthright. Thus, the clarity of the first option reflects the foundational legal principles of citizenship in the United States.