The story is about two old people named David and Rosy Jackson. Both of them had very bad memories. For example, Rosy would forget to cook dinner or take vegetables home after paying for them. David would show up for work on Sundays, thinking it was Monday. One winter they were to take a long plane trip. When they arrived at the airport, there were only ten minutes left. In that situation, anyone would get into the plane right away. But David and Rosy didn't do so. They went to buy some flight insurance  instead. Immediately after they put a two-pound note into a machine, their policy   came out. "Who would get the money if the plane crashed, I wonder?" asked Rosy. "My mother, of course," her husband replied. "We should post the policy to her. Now, be quick! Give me a stamp, will you?" he said to Rosy. "The plane is going to take off in another minute." David put the stamp on the envelope, dropped it into a postbox, and suddenly he let out a cry. What do you suppose happened to him? He had posted their plane tickets to his mother. Rosy is David's   _  .
friend mother sister wife