Karen has two kids, a boy and a girl, Dave and Nancy. Both of them are very lovely. And the boy loves his little sister very much because he thinks he must protect her. However, the little girl got a serious illness one day and needed some blood. And the hospital also couldn't find the same type of blood for the girl. But Karen knew both of her kids have the same type of blood. So Karen asked her son, "Would you like to give your blood to your sister?"
Dave agreed at once. After transferring his blood, the boy asked his mother, " Mom, how long can I live from now on?" Karen understood that her son had thought he would die soon after he lost some of his blood. So Karen said to her son, "Don't worry, my son. You won't die if you lose a little blood."
"Really? How long can I live?" the boy asked his mother again. "I think you can live to be 100 years old." smiled his mother. The boy lifted his arms and said happily, "Well, please give half of my blood to my little sister! Then both of us can live 50 years!"
