The correct answer is C. lively.
Exhilarating means exciting and stimulating. A lively speech is one that is full of energy and enthusiasm. It is likely to be well-paced and engaging, with a clear structure and interesting content. A boring speech, on the other hand, is one that is dull and uninteresting. It is likely to be slow-paced and rambling, with little to hold the listener’s attention. An irrelevant speech is one that is not related to the topic at hand. It is likely to be confusing and frustrating for the listener. A learned speech is one that is full of knowledge and information. It is likely to be dense and challenging, but also rewarding for the listener who is willing to put in the effort to understand it.
In the context of the question, the speaker is describing a speech that was exciting and stimulating. This suggests that the speech was lively and engaging. The other options are not as relevant to the description of the speech.