. They could11that a person died when his heart stopped beating. They learned, however, that the body did not die12when the heart stopped beating. They also discovered that humans remained alive13their brain remained active.
Today the difference between life and death is not as easy to see14in the past. Modern medical devices can15the heart beating and the lungs breathing long16the brain stops. But is this17？
The question has caused much debate18doctors in the United States. Many of them want a law that19a person is dead when the brain dies. A person would then be20dead when brain waves stop, even if machines can keep the body alive.
11. a. discover b. doubt c. convince d. see
12. a. immediately b. accidentally c. suddenly d. unexpectedly
13. a. even if b. before long c. long before d. as long as
14. a. as b. like c. such as d. the same
15. a. trace b. keep c. pursue d. increase
16. a. while b. afterward c. after d. before
17. a. alive b. life c. live d. lively
18. a. from b. about c. between d. among
19. a. insists b. claims c. says d. tells
20. a. decided b. considered c. determined d. estimated