The correct answer is D.
"What is the average income of a dentist in the United States?" is an appropiate question for research because it has only one possible answer. The average income can be calculated and through deep inquiring one can get the correct answer.
On the other hand, the rest of the questions may present different answers according to the person replying.
The appropriate research question is D. What is the average income of a dentist in the United States?
It should be noted that a research simply means an enquiry that's needed to get more information about an issue or topic.
In this case, the appropriate research question is "what is the average income of a dentist in the United States? This supports the stance that one should begin research by asking answerable questions rather than open-ended questions.
Learn more about research on:
https://brainly.com/question/968894
