The correct answer is D. Take an oath of loyalty to the United States.
Step-by-step explanation:
Naturalization is a process foreign people can complete to acquire the citizenship of a country, which allows them to have the same rights and protections of those who are born in that country. In the case of the U.S., this process requires multiple steps but the general last step in the process is to take the oath of loyalty or oath of Allegiance, which means the individual has been accepted to be a new citizen and he/she needs to the declare loyalty to the U.S. government and Constitution, as well as, acceptance of obligations as a citizen. According to this, option D is correct.