Critical Reasoning

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

The only option which supports the last line of the parent argument
"This
fact, however, does not indicate that most chickens
are immune to the virus that causes Ferber's
syndrome, since..................... "

is D. It is pretty evident from the options.

Hope you understand that only D can logically conclude 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.....................

We have to find a reason about why only cattle not chicken (commercially raised for meat) are affected by this disease when both are fed by the same feed.

Here are our options,

(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

'are not the only kinds' tries to bring in other types of animals and thus, out of scope since argument talks only about cattle and chicken.

(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

This option talks about animals contaminated with disease even when they are not fed with the contaminated feed. Thus, out of scope.

(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

This option talks about how resistance can be gained against the virus. Since nothing about resistance is described in argument, this is again out of scope.

(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

This talks about the time, which is more than a year, for the virus to become active. Thus, tries to justify why most chickens though fed with infected feed are not infected with the virus. This is because the meat is supplied to market in less than a year (which is less than the time required for the virus to become active). Thus, correct.

(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

The argument doesnot show any relation between the quantity of feed consumed and the chances of getting infected by eating the infected feed. Thus, incorrect.

Hope it helps.

Got it , Thanks a lot !