Which of the following does nut need to he considered in the area of heart valve replacement？
A. Rejection phenomena.
B. Anticoagulation.
C. Durability.
D. Regulatory bodies.
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What does "this dichotomy" in last paragraph refer to？
A. Cow's heart wall or pig's heart valve.
B. Tissues or device.
C. Housing or occuluder.
D. Anticoagulation or calcification.
It can be inferred from the passage that ______.
A. more than 30% of total rainfall can yield stream flow in the United States
B. the water in the entire eastern haft of U. S.A. goes beyond its necessary need
C. west part of U. S. A.doesn't have perennial yield of stream flow water
D. the yield of stream flow water is 'unevenly distributed in the United States
An eyewitness' testimony is sometimes inaccurate because______.
A. he is of the same race as the suspect
B. he is shown photos of many similar faces
C. he lacks the professional help from the police
D. he has a small number of suspects in the lineup
An inaccurate eyewitness testimony may lead to______.
A. the dismissal of the case
B. the disbelief in the court
C. the disrespect for the eyewitness
D. the conviction of an innocent person
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