根据短文内容，判断正误。
Whose Dogs?
Tom and his Mum walk in a street. They see a big dog and a small dog there.
"Tom, do you know whose dogs they are?" his Mum asks.
"Sorry, I don't know."
"The big dog is the small dog's Mum." says the mother.
"Oh, I know. The small dog is the big dog's son." answers Tom.
