题目选项分析

Which of the following most logically completes the argument?

Ferber`s syndrome, a viral disease that frequently affects cattle, is transmitted to these animals through infected feed. Even though chickens commercially raised for meat are often fed the type of feed identified as the source of infection in cattle, Ferber`s syndrome is only rarely observed in chickens. This fact, however, does not indicate that most chickens are immune to the virus that causes Ferber`s syndrome, since_____.

【选项】chickens and cattle take more than a year to show symptoms of Ferber`s syndrome, and chickens commercially raised for meat, unlike cattle, are generally brought to market during the first year of life