Susan is an American girl.
She is five years old.
She doesn't go to school and doesn't know how to read or write.
One day, her sister Lucy finds that she is at the table with a pen in her hand.
Lucy asks, "What are you doing?"
"I'm writing a postcard to my friend Betty" Susan answers.
"But you don't know how to write. " Lucy says.
"Well," Susan says, "Don’t you know Betty is only four years old, she doesn't know how to read either."