5 A: Sorry, we made so much noise last night. B: .....

Analysis:

The second speaker is responding to an apology for making noise. A polite and common response is to say 'Don't worry about it'.

Breakdown:

• A I understand: Possible, but less direct as a response to an apology.
• B Don't worry about it: Correct. This is a standard polite response to an apology.
• C I didn't realise it was bothering anyone: This implies the speaker was bothered, which is not the intended polite response.

Translated Question:

5 А: Прости, мы вчера так шумели. Б: .....