大牛请进，急需解释。

Benite

Lofgren's disease has been observed frequently in commercially raised cattle but very rarely in chickens. Both cattle and chickens raised for meat are often fed the type of feed that transmits the virus that causes the disease. Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease, however ,and chickens commercially raised for meat, unlike cattle, are generally brought to market during their first year of life.

Which of the following is most strongly supported by the information provided?


A, The virus that causes Lofgren's disease cannot bt transmitted to human beings by chickens.
B, There is no way to determine whether a checken is infected with the Lofgren's disease virus before the chicken shows symptoms of the disease.
C, A failure to observe Lofgren's disease in commercial chicken populations is not good evidence that chickens are immune to the virus that causes this disease.
D, An animal that has been infected with the virus that causes Lofgren's disease but that has not developed symptoms cannot transmit the disease to an uninfected animal of the same species.
E, The feed that chickens and cattle are fed is probabaly not the only source of the virus that causes Lofgren's disease.


求牛人解释。。。

shlshingse

Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease. Therefore, if a chicken is slaughtered before reaching his one year birthday, we would never know for sure he got the L-disease. Hence, C) is right.

hjbb1027

在另一个贴子里看到的解释:
B选项说：未发病之前没有办法断定鸡是不是有病。分析：有没有方法可以判断鸡得不得病不是文章得终点，终点在于逻辑推理的缺陷。即，未到发病期就杀了说鸡一定比牛难得这病，是不能接受得。                                                                  C选项说：没有查出鸡得病不能得出鸡有免疫力。正确，鸡没到发病期就杀了，当然是A failure to observe Lofgren’s disease,这肯定就不能断定说鸡比起牛难得病

hjbb1027

虽然我一开也选的是B，但是我觉得还是C更好点吧...
B is too broad to assume, there may be many scientific methods to determine whether chickens are affected by the disease that we dont know. So saying "There is no way to determine" is strong to assume.