We haven't heard from David (since he left Shanghai).(对括号部分提问) ——— ———haven't you heard from David?

We haven't heard from David (since he left Shanghai).(对括号部分提问) ——— ———haven't you heard from David?
We haven't heard from David (since he left Shanghai).(对括号部分提问) ——— ———haven't you hear
d from David?

We haven't heard from David (since he left Shanghai).(对括号部分提问) ——— ———haven't you heard from David?
How long
矢志提高答题准确率,一起努力吧^_^

Since when

what time

How long