Final answer:
True (option A), blood is typed and cross-matched with a potential donor before a transfusion to ensure compatibility and prevent transfusion reactions, unless in a life-threatening emergency where type O blood may be used.
Step-by-step explanation:
To avoid blood-type mismatches, blood is indeed typed and cross-matched to a potential donor before giving a blood transfusion. This statement is True. Blood type and cross-matching tests are crucial to ensure compatibility and avoid severe transfusion reactions. In non-emergency cases, only matching blood types are transfused. However, in life-threatening emergencies where there is not enough time for cross-matching, type O blood, known as the universal donor, may be used, although this can still pose risks if mismatched Rh factors are involved. Therefore, cross matching to determine blood type is always necessary before a transfusion unless an immediate life-threatening situation dictates otherwise.