Which one of the following does not affect the intonation?

Intonation refers to the variation in pitch when speaking, which conveys meaning and emotion. It is affected by voice/pronunciation, tone (rising or falling), and rhythm (pattern of stressed and unstressed syllables). Loudness (volume) is a separate prosodic feature that relates to how loud or soft one speaks, but it does not change the intonation pattern itself. Hence (4) Loudness is correct as the factor that does not affect intonation.