There are actually 4 blood forms: A, B, AB, or O. Also, blood is both Rh-constructive or Rh-detrimental. So if you have type A blood, It is really possibly A constructive or perhaps a detrimental. Which sort you happen to be is vital if you need a blood transfusion. https://www.youtube.com/watch?v=buIHtQY7fCU