Which of the following statements about tenor of discourse is correct().

A. It refers to the role of relationship in the situation in question: who the participants in the communication groups are and in what relationship they stand to each other.
B. It refers to the means of communication.
C. It refers to what is going on: to the area of operation of the language activity.
D. It refers to the type of language which is selected as appropriate to the type of situation.