OG详解-OG7 文法 Q10

Choice D is the best answer. The sentence identifies the type of scientist Chaudhuri is, noting that she is a sedimentologist. 
Choice A is incorrect. The sentence provides an example of a type of sedimentary rock; it doesn’t identify what type of scientist Chaudhuri is. Choice B is incorrect. The sentence indicates types of rock that some scientists study; it doesn’t identify what type of scientist Chaudhuri is. Choice C is incorrect. While the sentence states that some scientists study sedimentary rocks, it doesn’t identify Chaudhuri as this type of scientist.