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Tom is not old, but he does not have much hair. His wife Linda has thick and black hair. 

They have a son. His name is Jimmy, and he is six years old.

One day, Tom is reading a book in his room. Jimmy looks at his father for a long time and asks his mother, "Why does father have so little hair, Mum?" "He has little hair because he thinks a lot. He is a very clever man," Linda says with a smile.

"Then why do you have so much hair, Mum?" asks Jimmy.