I wanted to see Harry. How long ago ____
A) has he left ? B)did he leave ?
Which option would fit ?
I wanted to see Harry. How long ago ____
A) has he left ? B)did he leave ?
Which option would fit ?
You use the past simple, not the present perfect, with ago.
So the second sentence is Ok grammatically. How long ago did .....
However, you can use how long without ago in the present perfect.
A. How long ago did he leave?
B. Three hours ago.
A. How long has he left?
B. three hours.