Which of the Following Students Provides the Best Information Related

Which of the following students provides the best information related to the concept called common ground?

A) Raoul: "Common ground occurs when you want to show that you know more about a topic than other people in your group."
B) Cyd: "Common ground happens when one or more speakers make an ambiguous statement."
C) Ruth: "For people to achieve common ground,the speakers need to clarify misunderstandings."
D) Sam: "Common ground is relatively easy to establish,as long as people speak the same language."