OG详解-OG8 文法 Q13

Choice C is the best answer. The sentence emphasizes the aim, or goal, of the research study, noting what Terada set out to do: determine whether some of the Moon’s oxygen was coming from Earth. 
Choice A is incorrect. The sentence focuses on how the Kaguya satellite collected data; it doesn’t emphasize the aim of the research study. Choice B is incorrect. While the sentence mentions what Terada was curious about before conducting the research study, it doesn’t emphasize his study’s aim. Choice D is incorrect. The sentence presents the research study’s conclusion; it doesn’t emphasize the study’s aim.