英语翻译Mary smith was born in Toronto.When she was a student,sh

英语翻译
Mary smith was born in Toronto.When she was a student,she wanted to be a teacher,because she liked children.When she was twenty,she began teaching in a small school not far from her home.She was a good teacher ,and she laughed a lot with the children in her class,They enjoyed her teaching.
One day one of the girls in her class said to her,"Mary Smith,why does a man's hair become gray before his beard does?"
Mary laughed ang answered,"Sorry,I don't know.Helen,do you know?"
"I don't know.either,Miss Smith," said Helen."But it happened to my father." The other children in her class laughed when they heard this then a boy said,"I know,Miss Smith.A man's hair becomes gray first because it is sixteen years older than his beard."