Which of the following people would be the optimal donor for a 46-year-old woman with progressive chronic myelogenous leukemia who is scheduled to undergo allogeneic stem cell transplant
A: A human leukocyte antigen（HLA）-matched 42-year-old sister who has 3 children and no past medical history
B: An HLA-matched 44-year-old sister who has never been pregnant but has mild hypertension
C: 20-year-old daughter who has no medical problems and has never been pregnant
D: An identical twin who has never been pregnant
E: A 28-year-old cousin，male，who has no medical problems