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】resistance to some infectious organisms such as the virus that causes Ferber`s syndrome can be acquired by exposure to a closely related infectious organism