Here is a little puzzle for your students.
A young man went into a jewellery shop and said to the shop assistant, �Please can I have a potato clock?
�Well now, � answered the assistant, �we don �t sell those here. We sell alarm clocks, cuckoo clocks and grandfather clocks, but we don �t sell potato clocks. To be honest with you, I �ve never even heard of potato clocks. Are you sure you aren �t mistaken? �
�I �m quite certain �, said the young man, �I �m starting work tomorrow and my mother told me I would have to get a potato clock. �
What did the young man �s mum really say?