OG详解-OG3 文法 Q13

Choice C is the best answer. The sentence emphasizes both the duration (the length of time) and the purpose of Cohen’s and Rodrigues’s work by noting that the women have been working since 2003 to preserve Gullah culture. 
Choice A is incorrect. While the sentence emphasizes what visitors to Cohen’s and Rodrigues’s museums can learn, it doesn’t mention the duration or purpose of the women’s work. Choice B is incorrect. While the sentence emphasizes the purpose of Cohen’s and Rodrigues’s work, it doesn’t mention the duration of that work (the length of time the women have been working to preserve Gullah culture). Choice D is incorrect. While the sentence emphasizes where and when Gullah culture developed, it doesn’t mention the duration or purpose of Cohen’s and Rodrigues’s work.