OG6 阅读 Q14

Choice C is the best answer. In lines 23-25("be... explain it"), the passage states that "there is not always common agreement about what the public needs to know." In this context, a "common" agreement is a widespread one shared by many people. 
Choices A, B, and D are incorrect because in the context of something shared by many people, the word "common" implies that it is widespread, not that it is plentiful or abundant (choice A), recognizable to others (choice B), or normal (choice D).