This question asks you to identify the principal purposes of each passage, and find the purpose that they have in common. When you get a question like this, start by reading each passage and trying to spot the purpose for yourself before turning to the answer choices.
Passage A discusses blues musicians in comparison to griots, placing their music in the context of history (slavery). Passage B discusses the social status and history of griots and explains what their music was used for.
Now, turning to the answer choices: (A) is incorrect because there is no discussion in either passage as to how music can replace institutions.
(B) is incorrect because these passages are not about a cultures' values but rather about how music fits into different cultures and histories.
(C) is incorrect because we are never told that griots and blues musicians are closely related musical traditions. Rather, passage A tells us that "one could hardly find two performers with less in common." (line 4)
(D) is correct because it reflects the point we identified above. These passages are placing the musicians in historical context, namely in the context of their social standing.
(E) is incorrect because passage B does not criticize any characterization of the griots. While passage A starts off by saying that many commentators are wrong about the relationship between griots and blues musicians, the question is about both passages, and passage B does not fall into this pattern.
