There is a student from China in our class. He is very good at his lessons, but he is also very shy. He doesn't talk too much with us because he thinks that there are so many differences. When he comes into our classroom for the first time, he is so frightened（受惊的） that he crys.

    That's because our appearances（外表） are different. For example, his hair is short, black and straight, but ours are all different from his. Jim's hair is yellow and much longer than his. Dave's hair is curly and brown. Kitty's hair is blonde. Our builds and clothes seem to be strange in his eyes, too. Peter is a boy. He is tall and thin, but he often wears a colorful T-shirt.

    Some boys like wearing the same kinds of clothes as girls, and some of them have long hair. So sometimes it's difficult to tell whether（是否）they are boys or girls. Today is Sunday. I have a walk with my grandmother in the park. My grandmother is 80 years old and she can't see well. After some time, my grandmother is tired（疲倦的）, so she sits down on a chair. There is another person sitting on the chair, too.

    "Hello," my grandmother says to the person with long hair next to her. "Can you see the person with long hair under the big tree? Is it a boy or a girl? "

    "Which（哪一个） one?" asks the person.

    "The one eating under the big tree," says my grandmother.

    "The boy?" says the person. "He's my brother Mark."

    "Oh," says my grandmother, "I don't know you are his sister."

    "No, I'm not his sister. I'm his brother."

要求：包含以上所有信息，语句通顺，合乎逻辑，50词左右。