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　　雅思写作常用的语法练习-广州朗阁雅思培训中心
　　Complete the following sentences by circling the missing words.
　　1 .Science still a cure for cancer.
　　a. doesn’t find c. hasn’t found
　　b. haven't found d. aren’t finding
　　2. While he_a route to the Indies, Columbus discovered America.
　　a. searched c. had searched for
　　b. was discovering d. was searching for
　　3. Existing reserves of fossil fuel_by 2045.
　　a. have been run out c. is going to be run out
　　b. will have run out d. have run out
　　4. If logging of tropical rainforests continues at the present rate,_a
　　30 per cent increase in atmospheric CO2 by the year 2000.
　　a. there will be c. there would be
　　b. there might have been d. there could not have been
　　5. Only妙investing heavily in value-added exports_如m the
　　present trade imbalance.
　　a. the country can emerge c. can the country emerge
　　b. the country might emerge d. the country emerged
　　6. The mystery of the double helix_，the scope for genetic engineering
　　dramatically increased.
　　a. having solved c. solving
　　b. having been solved d. solved