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3.A.puts          B.equipping        C.places        D.placing

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2.A.where     B.what            C.which        D.when

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1.A.from         B.in              C.of          D.with

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20. A. on        B. in          C. by          D. with

(6)

Scientists in the United States are using teat-tube baby techniques to try to save wild animals ____1_____ extinction(灭绝).

The test-tube technique, or in-vitro fertilization, ____2_____ involves fertilizing eggs(使卵子受精)in the laboratory and then ____3___ them inside the female, became famous when human babies were conceived(怀孕)in this way. The technique is now helping another mammal---the tiger. __4____ the process is successful, it could prevent many species dying ____5_____ . At Minnesota Zoo, in the US, scientists have taken semen from a male tiger and eggs from a female tiger, and ___6_____ them together in the ____7_____. These men fertilizes the eggs and, after a period of about 36 hours, the new embryos(胚胎)can be implanted in the uterus(子宫)of a tigress. This technique ____8_____ the baby tiger to develop naturally ____9_____ the uterus.

A big ____10_____ of this method is that the female tiger does not even have to be the same ___11____ as the embryo. The zoo team found ____12_____ could use a Siberian tiger as a surrogate mother(替身母亲)for Bengali tiger embryos. The test-tube tiger technique could  ____13_____ in a bank of embryos of ____14_____ animals. An embryo store would help ____15__ a healthy genetic mixture within _16_____ groups of animals.

Many species today are threatened by hunting, or by the ____17_____ of their habitat(居住环境)and food chains. Threatened animals are often _  18  _____ in numbers and left in isolated groups. Away from other herds or family groups of their own kind, they are ____59_____ to breed with close relatives(近亲繁殖)and this produces many more unhealthy off-spring (后代)than ____20_____ normally occur.

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19. A. foods       B. grains        C. meats         D. fruits

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18. A. by        B. to           C. as           D. for

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17. A. related       B. concerned       C. charged         D. decided

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16. A. grades     B. warnings        C. cautions        D. tricks

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15. A. caught       B. shared         C. divided        D. separated

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14. A. believed    B. accepted        C. ensured        D. found

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