What did you think of the lecture?
I thought it was very interesting.
Did you really?
Yes, didn't you?
Certainly not. I thought he talked a lot of rubbish.
So you think you know more than he does.
Well, take coal for instance.
What about it?
Coal won't become important again.
Why not?
It's too dirty. They won't be able to find people to work down coal mines in the future.
They'll invent new kinds of machinery.