A．It is the major ingredient for human evolution.
B．It is a medium that binds all human beings.
C．It is the most popular means for communication.
D．It is only used for the purpose of enriching knowledge.

A．By changing the speed of speaking.
B．By using different dialects.
C．By changing the tone at the proper time.
D．By making faces.

A．It will make your speech concise.
B．It will save your time.
C．It will make the recitation of the speech easy.
D．It will avoid grammatical mistakes.