Mr. Gao lives in a town. When he was twenty-five, his son was born. He calls him Gao Ling. The little boy is clever. He and his wife love him very much. It's September 1st today. A new school year begins. Gao Ling is happy and wears his most beautiful clothes. He's going to school with his new bag. "Let me take you to school, dear." said Mrs. Gao. "Thank you, Mummy," said the boy. "The school is not far from here.I can go there myself." At school a teacher met the little boy and asked, "What's your name, my little friend?" "Gao Ling, sir." answered the boy. "How old are you?" "Six, sir." "What's your father's name?" "Gao Daling, sir." "How old is he?" "He is six, too, sir." "Oh," the teacher said in surprise. "Is he as old as you?" Yes, sir," said the boy. "He became a father only on the day when I was born." Gao Ling didn't let his mother take him to school because  _  .
she was too busy his friends could took him the policeman could help him the school is near and he could take care of himself