Correct answer: d. is a citizen of another country legally residing in the United States.
Explanation:
If you think about the term, "resident alien," the answer is essentially spelled out by that term. The person is an "alien," which means someone from another country (not a US citizen). At the same time, the person is a "resident," which means the individual is residing in this country.
If an immigrant is living in the country illegally, we call that person an "illegal immigrant" (just like the description).
If a person was born in the United States, that person is a US citizen.
Also, someone born in another country that has been naturalized is also a US citizen.
