Mr. And Mrs. Bell are very forgetful . For example , Mr. Bell sometimes goes to his office for work on Sunday morning, for he thinks it is Monday. And Mrs. Bell sometimes forget to cook supper for the family.  One summer they planned to fly to New York for their holidays. They got to the airport only ten minutes before the plane took off. So time was short. But suddenly Mrs. Bell said she must tell Alice, their daughter, not to forget to lock the front door when she went to school. As Alice was then at school, they couldn't tell her about it by telephone. So they hurried to the post office. Mrs. Bell wrote a short note to Alice while Mr. Bell bought a stamp and an envelope . Soon the note was ready. They put the stamp on the envelope in a hurry and dropped it in the letter box, but suddenly Mrs. Bell began to cry. The short note was still in her hand. She had put the plane ticket in the envelope. Mr.and Mrs. Bell wrote a note to their daughter to tell her  _
that they had a good journey to lock the front door that the couldn't fly to New York to take good care of herself