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  3. Ragwort was accidentally introduced to New Zealand in the late nineteenth century and, like so many invading foreign species, qu

Ragwort was accidentally introduced to New Zealand in the late nineteenth century and, like so many invading foreign species, qu

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问题 Ragwort was accidentally introduced to New Zealand in the late nineteenth century and, like so many invading foreign species, quickly became a pest. By the 1920s, the weed was rampant. What made matters worse was that its proliferation coincided with sweeping changes in agriculture and a massive shift from sheep farming to dairying. Ragwort contains a battery of toxic and resilient alkaloids: even honey made from its flowers contains the poison in dilute form. Livestock generally avoid grazing where ragwort is growing, but they will do so once it displaces grass and clover in their pasture. Though sheep can eat it for months before showing any signs of illness, if cattle eat it they sicken quickly, and fatality can even result.
The passage implies which of the following about the problems ragwort poses to dairy farmers?
选项 A、Milk produced by cows that eat ragwort causes illness in humans who drink it.
B、Ragwort can supplant the plants normally eaten by cattle.
C、Cattle, unlike sheep, are unable to differentiate between ragwort and healthy grazing.
答案B
解析 Choice B is correct. The question asks about the problems ragwort poses to dairy farmers.
Choice A is incorrect: The passage does not mention the effect of ragwort consumption on the milk produced by cows.
Choice B is correct: The passage mentions that livestock will eat ragwort "once it displaces grass and clover in their pasture."
Choice C is incorrect: The passage claims that "livestock generally avoid grazing where ragwort is growing," but does not make a distinction between cattle and sheep.
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