Explanation
Correct answer: D.
Choice D is the best answer. This choice effectively specifies who may have first populated the Azores, according to the 2015 study: the Vikings.
Why the other choices are wrong
Choice A
Choice A is incorrect. This choice doesn’t effectively specify who may have first populated the Azores, according to the 2015 study. It only mentions the historical belief that the Portuguese were first. The 2015 study drew a different conclusion.
Choice B
Choice B is incorrect. This choice casts doubt on the Portuguese claim but doesn’t name the group of people who may have arrived before the Portuguese.
Choice C
Choice C is incorrect. This choice mentions the evidence that the researchers found but not the conclusion they drew from it. It doesn’t name the possible group of people who may have arrived before the Portuguese.