Final answer:
Dr. Washington was using a transition cue to notify his audience of the shift to a new topic within his lecture, which serves to keep the audience engaged and aware of the lecture's structure.
Step-by-step explanation:
During the lecture, Dr. Washington used a transition cue, which is an important component in structuring oral presentations and written works. Transition cues help the audience to follow the logical progression of ideas by signaling a shift from one topic to another. In this particular case, Dr. Washington's announcement of moving on to his fourth topic is a clear example of a lecture cue used to guide listeners through the structure of his speech.
This type of cue is not only useful in spoken communication but also plays a crucial role in written texts, where transitions signal changes in argument or topic to maintain the flow of ideas.
Effective use of transitions, such as those underlined in provided examples, ensures clarity and cohesion in the organization of content, making it easier for the audience to follow and understand the speaker's or writer's key points.