Question

Australia's worst pests（害蟲）are the rabbits, ______ by a settler who released 24 into the wild for sport hunting. In less than 100 years, the rabbits grow into the millions of ones, leaving large areas of land looking like the surface of the moon due to thousands of rabbit caves. The spread of the rabbits in Australia was the fastest of all animals in the world. The spread of the rabbits' _______in 1950 cut the number, but it was not until 1997 when the spread of another disease targeted the pests that the number was finally brought under control. Farm losses due to rabbits today still ______ a surprising total A $200 million （US $112 million）a year.

The European red foxes, also released for sport hunting, are growing and eating sheep flocks, costing farmers A $40 million（US $22. 4 million）a year. The State of Victoria ______ a A $10（US $5. 6）prize for each fox tail and has gathered 25,000 in a few months.

Foxes are one of the biggest threats to wildlife in Australia. Foxes kill thousands of lambs, birds and native wildlife.

Now the government is paying more attention to this problem. Scientists ______ that they should import some wild dogs, which are natural enemies of rabbits and foxes. But how to control their ______ is also a problem. Scientists say they will not take any big action until they are sure not to bring another ecological（生態(tài)的）problem.

1.A.discovered B.introduced C.shown D.killed

2.A.sadness B.struggle C.disease D.tiredness

3.A.kept B.remained C.left D.pushed

4.A.catches B.includes C.offers D.collects

5.A.suggest B.solve C.discover D.explain

6.A.letter B.name C.note D.number

Answer 1