In speech, when words or sentences are ambiguous, gesture and tone of voice are used to indicate the intended meaning.
Conditional / Causal (When Z, X is used to do Y)
If words or sentences or ambiguous, Gesture / tone of voice >> intended meaning
Contrast
Writers don't have that option.
Causal (X is used to detect Y)
Arrangement of words/sentences >> intended meaning
Evaluate
The #1 thing we read for on Most Supported is causal relationships, and this paragraph was stressing different ways that speakers/writers can cause an audience to grasp their intended meaning.
Goal
Look for the most provable answer. It will probably reflect the fact that we learned of two different ways (gestures/tone vs. stylistic arrangement of words/sentences) to communicate intended meaning.