The answer in the blank is common themes. It is because using common themes or including them on the speaker's speech could make the audience relate on the topic and to be intrigued or to be interested. With this method, not only will the speaker give out his information but he or she could capture the attention of the audience.
A speaker can invoke concepts or ideas that the audience is already familiar with by including common themes in a speech.
Explanation:
When a person is going to give a speech in front of a big audience, it is necessary to add some points of neutral or common information to which if not everyone, as many as possible can relate so the concepts can be easily invoked because they understand and the speaker can convey the message and achieve the objective.
