Final answer:
Type O negative blood is used for transfusions when the patient's blood type is unknown to prevent adverse reactions. If agglutination occurs with both anti-A and anti-B antibodies, the patient's blood type is AB positive.
Step-by-step explanation:
In emergency situations like a motor vehicle accident where a patient presents with multiple traumatic injuries and severe bleeding, there may not be enough time to determine their blood type before a transfusion is needed. In such cases, the patient is transfused with Type O negative blood, commonly known as the universal donor type, because it lacks A, B, and Rh antigens and thus has the least potential for causing an adverse reaction in all patients. It is essential for avoiding a hemolytic transfusion reaction, which can be life-threatening. On the other hand, if both anti-A and anti-B antibodies cause agglutination in a blood typing test, it indicates that the patient has AB positive blood type, the universal recipient, as their blood contains both A and B antigens.