Final answer:
Hyphens should be added between 'really' and 'knew' as well as between 'to' and 'listen'.
Step-by-step explanation:
The correct answers are b. really knew how and c. to listen. In the sentence, hyphens should be added between the words 'really' and 'knew' (b) and between the words 'to' and 'listen' (c).
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