When you donate blood, it can be used for blood transfusions. Transfusions are common during certain surgeries or when a person has an injury that causes blood loss. The O blood type is considered to be a universal donor because a person with any blood type can receive it. However, people with the O blood type can receive blood from only those with the same blood type. Why do you think this is so? What blood type would be the universal recipient (meaning the person can receive blood from any blood type)?