The correct answer is C. uncivilized.
A barbarian is a person who is considered to be uncivilized or primitive. The term is often used to describe people who live in a different culture or who have different customs than the speaker. In the context of the question, the inhabitants of the island are described as barbarians because they are not part of the speaker’s culture and they have different customs.
The other options are incorrect because they do not accurately describe the inhabitants of the island. Option A, civilized, is incorrect because the inhabitants of the island are not considered to be civilized by the speaker. Option B, cruel, is incorrect because there is no evidence that the inhabitants of the island are cruel. Option D, bad, is incorrect because there is no evidence that the inhabitants of the island are bad.
It is important to note that the term barbarian is often used in a derogatory way. It is important to be sensitive to the fact that this term can be offensive to some people.