While Albert Einstein 1) ……………… (go) around the USA on a speaking tour, his driver often 2) ……………….. (enter) the hall where Einstein 3) …………………. (give) his lecturers, 4) …………….. (sit down) in the back row and 5) …………………(listen) to the lecture. One day the driver 6) ………………(say) that he could probably give the lecture himself because he 7) ………………… (hear) it so many times. Sure enough, at the next stop on the tour, Einstein and the driver 8) ………………….. (switch) places. Einstein 9) ………………… (sit) at the back of the lecture hall in the driver’s uniform and the driver 10) …………………… (stand) on the stage. After a driver 11) …………………. (give) a brilliant lecture, a member of the audience 12) ………………… (ask) him a difficult question. “Well, the answer to that question is quite simple,” he 13)…………………… (reply) casually. I bet my driver, who is sitting at the back there could answer it ….”