Translation:The nurse waits until he stops singing.
Because đ /ɗ/ is implosive. https://en.wikipedia.org/wiki/Voiced_alveolar_implosive
Is there some substantial difference between ‘waits for him to stop’ and ‘waits until he stops’ that got the former rejected?
Maybe they wanted us to nail down the "đến khi" part. But otherwise they seem equivalent.