The correct answer is (A).
Getting to the Answer: When asked about the function of a phrase, look a few lines before and after to get a sense of what the author is trying to convey to the reader. Here, the author is talking about a memory that he now realizes is inaccurate, so look for an answer that describes the discovery of something deceptive.
(A) Correct: this correctly summarizes the main idea of the paragraph
(B) Incorrect: this does not correctly summarize the paragraph because the paragraph does not talk about modern Pueblos' beliefs
(C) Incorrect: this distorts the ancient Pueblos' belief; the happiness of humans does not play a part in the coming rain
(D) Incorrect: although the paragraph says that the Sky will bless the Earth, it does not state that the Earth is more dependent on the relationship than the sky