What type of speaking requires the speaker to engage with the audience spontaneously?

The correct answer is impromptu speech, which is characterized by the speaker's need to respond spontaneously to a prompt or topic without prior preparation. This type of speaking typically arises in situations where quick thinking and articulation are required, such as during class discussions, speeches in response to unexpected questions, or any context where immediate verbal communication is necessary.

The emphasis on spontaneous engagement means that the speaker relies on their knowledge, experience, and quick analytical skills to convey their message effectively. This format can showcase a speaker's ability to think on their feet and can help convey authenticity and dynamism in communication.

In contrast, formal speech usually involves thorough preparation and a structured format, aimed at delivering a well-rehearsed message. Extemporaneous speech also requires some degree of preparation but is delivered in a more conversational manner, relying on notes and an outline rather than spontaneity. Debate speech involves prepared arguments and strategies for opposing viewpoints, rather than spontaneous interaction with the audience.