A particular lecturer gives an annual public lecture at a certain place, and each time he goes, the people give him a rousing welcome without much fuss.
This always bothers the man and he wants to avoid it. So during the year in the question, the man employed a driver who looked exactly like him. He told the driver to wear his clothes and deliver the lecture so that he can avoid the rousing welcome.
When it got to question time, the driver was asked a particular question that was beyond his knowledge and he didn’t want to disgrace his master so he smiled and said, ” that is a simple question, indeed, and to prove this to you, i will call my driver to answer it” So the real lecturer answered the question but people didn’t get the trick.