Which of the following is an example of an impromptu speech?

An impromptu speech is characterized by being delivered with little to no preparation or prior notice. This type of speech often arises spontaneously and requires the speaker to think on their feet, responding to a topic or prompt immediately. This is different from a rehearsed presentation, which involves prior preparation and practice, allowing the speaker to deliver the content more smoothly. Similarly, a memorized lecture is a speech that has been carefully planned and practiced beforehand, as is a scripted announcement, which typically follows a prepared script. The uniqueness of an impromptu speech lies in its immediacy and the speaker's ability to articulate their thoughts in the moment, making "a speech given without prior notice" the correct identifier for this particular form of communication.