Why did the sugar cane farmers bring cane toads to Australia?

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问题 Why did the sugar cane farmers bring cane toads to Australia?
  
Perhaps the most unusual animal ever brought to Australia was the cane toad. It is a large and ugly species of toad and was imported to this country by sugar cane farmers in 1935 [18B] to get rid of the beetles which killed the sugar cane plants.
    The cane beetle is the natural enemy of the sugar cane plant. It lives in the cane and drops its eggs onto the ground around the base of the cane. The eggs develop into worms and then the worms eat the roots of the cane, resulting in the death of the plant. In the mid 30s there was a serious outbreak of cane beetles and the farmers became desperate to get rid of the pest which was ruining their livelihood.
    Meanwhile it was reported that a toad, native to Central America, had been taken to Hawaii, where cane is also grown, and introduced with apparent success. So the Australian farmers arranged to import one hundred toads from Hawaii. The toads were then released into the cane fields to kill cane beetles.
    As predicted, the toads started to breed successfully and within a very short time their numbers had swollen. But there was one serious problem. It turned out that [20A] cane toads did not eat cane beetles. And the reason for this is that toads live on insects that are found on the ground and the cane beetle lives at the top of the cane plant well out of reach of the toads. In fact they never come into contact with each other.

选项 A、The cane toads did not eat the cane beetles.
B、The number of the cane toads had swollen.
C、There was another outbreak of the cane beetles.
D、The cane toads killed all the cane beetles.

答案A

解析 短文结尾提到,澳大利亚看到夏威夷蔗农的成功样例后,决定引入蔗蟾,但是引入之后,问题也出来了,那就是蔗蟾(cane toads)并没有吃蔗虫(cane beetles),故答案为[A]。
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