The correct answer is D. A main idea that is not stated in the speech
Step-by-step explanation:
In speeches, the main idea is the point the speaker wants the audience to understand. Due to this, the main idea is always supported by the details the speaker includes and the general structure in the speech. Additionally, the main idea can be explicitly stated as the speaker might mention the main idea either during the introduction, body or conclusion of the speech. But in some cases, the main idea is not stated but only explained through details and therefore it is considered as implied.