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
identi� ed 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.....................

(A) chickens and cattle are not the only kinds of
farm animal that are typically fed the type of
feed liable to be contaminated with the virus that
causes Ferber's syndrome
(B) Ferber's syndrome has been found in animals
that have not been fed the type of feed liable to
be contaminated with the virus that can cause
the disease
(C) 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
(D) 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 � rst year of life
(E) the type of feed liable to be infected with the
virus that causes Ferber's syndrome generally
constitutes a larger proportion of the diet
of commercially raised chickens than of
commercially raised cattle


OA is D ? Need help understanding the answer.

Help appreciated