In England nobody under the age of eighteen is allowed to drink in a public
Mr.Thompson used to go to a bar near his house quite often，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 first time．They drank for
half an hour，and then Mr．Thompson said to his son，"Now，Tom，I want to teach you a
useful lesson．You must always be careful not to drink too much．And 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 have become four，you've had enough and
should go home．"
"But，Dad，"said Tom，"I can only see one light at the end of the bar．"