The correct answer is D.
A non-citizen national is a person born or with ties to the outlying U.S. possessions of American Samoa and Swains Island. The same applies also to people born in Northern Mariana Islands.
Non-citizens nationals are allowed to reside and work in the United States without restrictions. They are protected by the U.S. Constitution but are not granted the same rights as U.S. citizens. They are not allowed to vote in federal or presidential elections but they can vote for a their delegate in the House of Representatives. Some Social Security programs are also unavailable to them.
All U.S. citizens are U.S. nationals but not every U.S. national is an AMerican citizen.