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
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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
Which of the following is true？
A. Water evaporated to atmosphere is unavailable to man because it is from useless plants.
B. Man can interfere with water evaporation by growing some plants.
C. Man can recycle evaporated water to grow useful plants.
D. Useful plants can collect the evaporated water which will be used for other purpose.
Which of the following can be classified as a mechanical valve？
A. Tilting disc device.
B. Aortic valve.
Collagenous tissue.
D. Porcine valve.
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