In England nobody under eighteen years old is allowed to drink in a bar.Mr Thompson often went to a bar nearby.But he never took his son，Tom，because he was too young.Then when Tom had his eighteenth birthday, Mr Thompson took him to his usual bar for the firsttime. They drank for an hour. Tom drank a lot, then Mr Thompson said to his son, "Now, Tom, I want to teach you a useful lesson. How do you know when you' ve had enough? Well, I' ll tell you. Do you see those two lights at the end of the bar? When they seem to become four, you ve had enough and should go home. "
"But Dad."said Tom, "1 can only see one light at the end of the bar."