The correct answer is (C).
This question belongs to the "Summarizing the Main Conclusion" prototype of critical thinking questions.
The key to getting the answer right in this type of question is reading between the lines and not looking for an explicit, superficial, and sometimes irrelevant, summary of the passage.
The argument's main conclusion is, in most cases, not an extract of the passage or a possible generalization of it. It is rather an implicitly written inference that stems for the data presented.
You must reject all conclusions that are either false (clearly contradicted by information in the passage), superficial, or irrelevant. Irrelevant means that the information in the answer choice could be correct but it is not a conclusion one could logically draw from the information given.
The passage provides a brief story. Read it quickly and mentally map the vital information: a 4,000 year-old body was found in Greenland. The body belonged to the Saqqaq people (later Eskimos). The Saqqaqs descended from the Chukchis of Siberia.
Think: in order for the last sentence to be true, that the Saqqaqs of Greenland are most closely related to the Chukchis of Siberia, what must be true? That there was a migration at least 4,000 years ago from Siberia to Greenland.
Answer choices A, B, D, and E are irrelevant. The passage is not about the cultural relation between the Chukchis and the Eskimos (A); it is not about where DNA is best preserved in the body (B); or when Greenland became populated (D); or Eskimo customs (E).
Answer choice C, on the other hand, can be correctly concluded: There was a migration across the continent from Siberia to Greenland more than 4,000 years ago. If the Greenlander belonged to the Saqqaqs, and the Saqqaqs' closest relatives live in Siberia, then it follows that there was a migration at least 4,000 years ago from Siberia to Greenland.
Therefore, the correct answer is C.
Learning how to distinguish between the elements mentioned above is of the prime purposes of this practice pack. Training will definitely help you eliminate classic distractor-traps that were efficiently constructed by the test writer.