Lofgren’s disease hasbeen observed frequently in commercially raised cattle but very rarely inchickens. Both cattle and chickensraised for（上交） meat are often fed thetype of feed that transmits the virus that causes the disease. Animals infected with the virus take morethan a year to develop symptoms of Lofgren’s disease, however, and chickenscommercially raised for meat, unlike cattle, are generally brought to market during their first year of life.
Which of the following ismost strongly supported by the information provided?
A. The virus that causes Lofgren’s disease cannot betransmitted to human beings by chickens.
B. There is no way to determinewhether a chicken is infected with the Lofgren’s disease virus before thechicken shows symptoms of the disease.
C. ！Afailure to observe Lofgren’s disease in commercial chicken populations is notgood evidence that chickens are immune to the virus that causes this disease.
D. An animal that has been infected with the virus that causesLofgren’s disease but that has not developed symptoms cannot transmit thedisease to an uninfected animal of the same species.
E. The feed that chickens and cattle are fed is probably notthe only source of the virus that causes Lofgren’s disease.
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发表于 2011-7-19 17:13:26
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