Marty is five years old，and he is the baby of the family．

    His brother Ralph likes playing basketball．"Can I play,too?"asks Many．

    "No,Marty．The basket is too high for you，and the ball is too big for your baby hands，"says Ralph．

     "I'm not a baby,"Marty says．"I'm 115 cm!"

     Then Marty sees his sister Cindy riding her bike．She'll go to the bookshop．

    "Can I ride to the shop，too?"asks Marry．

    "No，the shop is too far．And your baby bike is too slow．"

    "I'm not a baby,"Marty says．"I'm nearly(接近)six."

    "Six?"says Cindy．"You just had your fifth birthday last Friday!"

    Marty starts to cry．"Why do you cry,dear?"asks Marty's mother．

    "I'm too young to do anything．I don't want to be the last child."

    His mother pats(轻拍)his belly(肚子)and says，"We will have the fourth child．And that is to say,you'll be a big brother．"

    "But．I'm too small to be a big brother,"Marty says．"I'm just a baby!"

根据材料内容选择最佳答案。