In which aspect is intonation primarily involved?

Intonation refers to the variation in pitch while speaking, which plays a critical role in conveying meaning and emotion in language. It is particularly associated with sentence-level pitch variation, impacting how statements, questions, and emotions are expressed. For instance, rising intonation often indicates a question, while falling intonation may signal the end of a thought or statement. This use of pitch variation is essential for conveying nuances in conversation, such as sarcasm or emphasis, which are often tied to the overall structure of sentences rather than individual sounds or word parts.

The other aspects listed, such as word-final sounds, individual vowel sounds, and initial consonant clusters, pertain more to phonetics or the production of specific sounds rather than the overarching patterns of pitch that characterize intonation. These elements do not influence the overall melodic quality of sentences in the way that intonation does, which is why sentence-level pitch variation is the most accurate representation of intonation's primary involvement.