Which of the following best defines speech?

The best definition of speech in this context is centered on the verbal aspect of communication. Speech specifically involves the use of spoken language, where individuals articulate sounds and words to convey a message. This definition highlights the auditory nature of speech, setting it apart from broader concepts like language or communication, which may include non-verbal forms such as sign language or written communication.

When considering the other choices, while they touch upon aspects of communication and language, they do not capture the essence of speech itself. The first choice, for example, discusses the exchange of messages, which could occur non-verbally and doesn't solely pertain to spoken language. Similarly, the second option focuses on the conventions of language use in social contexts, emphasizing social norms rather than the actual production of speech. Lastly, the fourth choice relates to the shared rules of representing ideas, which aligns more closely with the study of language rather than the act of speaking. Thus, the emphasis on verbal exchange in the chosen definition is paramount in accurately describing what speech entails.