阅读短文，选择正确答案。

It is Tuesday today. Boys and girls are all at school. They usually come to school by bus. Their teacher is at school too. The English teacher's name is Gu Yan. She is young. She usually comes to school on foot. Look at the classroom of Class One, Grade Four. In this room, you can see a boy and a girl. The boy is eleven. His name is Jack. The girl is Emma. She is twelve. John is Jack's friend. He is an American boy.