Answer:
D
Step-by-step explanation:
Hyphens are used to connect two words in order to act as one word. A good rule of thumb is if two words separately communicate their words correctly then they do not need a hyphen.
When looking at our answer choices, we can see in D that the terms "un" and "American" cannot both stand alone because "un" has no meaning on its own. This means that a hyphen should connect the two, making D the correct answer here. Hope this helps!