Final answer:
A critical trauma patient would receive Type O negative blood in an emergency transfusion because it is universally accepted by all blood types without adverse reactions.
Step-by-step explanation:
In the case of a trauma patient following a motor vehicle accident with multiple traumatic injuries and severe bleeding, the patient would be given Type O negative blood if there is no time to determine their blood type. Type O negative blood, often known as the universal donor blood type, is used because it lacks antigens on the red blood cells and can be safely accepted by individuals of all blood types without causing an adverse reaction. This emergency transfusion can be life-saving while further blood typing or cross-matching is performed.