Sometimes you can only ask questions at the end of a presentation. In that case, you need to refer back to the point in the talk you need clarification on. Here are some useful expressions to help you do that:
First focus on the point you want to discuss
You talked about
You talked about the problems with the Glasgow office.
You told us about
You told us about the success of the new Singapore plant.
You dealt with
You dealt with the difficulties with the new system quite quickly.
You described the reaction of the workers to the changes as 'broadly positive'.
You commented on
You commented on the problems with the euro.
You referred to
You referred to the poor economic outlook.
You mentioned the drop in sales in Europe.
Then ask for clarification
Could you tell us
Could you tell us why you did that?
Could you tell us if you think that was the right thing to do?
Could you explain
Could you explain why you said that?
Could you explain the thinking behind that?
These set phrases can be very useful
Could you be a bit more specific?
Could you give us more details?
Could you elaborate on that?