In response to viral infection, the immune systems of mice typically produce antibodies that destroy the virus by binding to proteins on its surface. Mice infected with a herpesvirus generally develop keratitis, a degenerative disease affecting part of the eye. Since proteins on the surface of cells in this part of the eye closely resemble those on the herpesvirus surface, scientists hypothesize that these cases of keratitis are caused by antibodies to herpesvirus.

Which of the following, if true, gives the greatest additional support to the scientists’ hypothesis?

A. Other types of virus have surface proteins that closely resemble proteins found in various organs of mice.
B. There are mice that are unable to form antibodies in response to herpes infections, and these mice contract herpes at roughly the same rate as other mice.
C. Mice that are infected with a herpesvirus but do not develop keratitis produce as many antibodies as infected mice that do develop keratitis.
D. There are mice that are unable to form antibodies in response to herpes infections, and these mice survive these infections without ever developing keratitis.
E. Mice that have never been infected with a herpesvirus can sometimes develop keratitis.

Please explain each answer choice.
_________________

You want something, go get it . Period !

+1 D

A. Other types of virus have surface proteins that closely resemble proteins found in various organs of mice. (Then why just eyes are affected, eliminate)
B. There are mice that are unable to form antibodies in response to herpes infections, and these mice contract herpes at roughly the same rate as other mice. (This weakens the hypothesis)
C. Mice that are infected with a herpes virus but do not develop keratitis produce as many antibodies as infected mice that do develop keratitis. (Irrelevant)
D. There are mice that are unable to form antibodies in response to herpes infections, and these mice survive these infections without ever developing keratitis. (This is our answer, since they do not develop antibodies they do not develop keratitis)
E. Mice that have never been infected with a herpes virus can sometimes develop keratitis. (This weakens the hypothesis)


_________________

First Attempt 710 - first-attempt-141273.html

Yea Rocky :D , we did it ! hah
_________________

You want something, go get it . Period !

This is a typical strengthen cause and effect problem -

We need to show that only X can lead to the result Y or eliminate any other alternate causes that lead to result Y.

If the cause does not occur then the result does not occur ; Hence , If the cause is there the result is also there.

thanks,
Ankit
_________________

You want something, go get it . Period !

Hey Gyan!! Nice explanation. I had a tough time understanding this question. Finally my teacher helped me. But I was still confused and could not explain him my problem.
I decoded this prob in the following manner:-

Virus hits mouse - mouse develops antibody (antibody hooking onto protein on virus destroys virus). Now, protein on eye = protein on (herpes)virus. (So, because an antibody might get confused between the two - this was terrific comprehension of the hypothesis) the antibody (hooking onto protein on eye ) leads to keratitis.
Hence, herpesvirus - antibody - keratitis.

My doubt is that how can we strengthen this by saying that (there are mice => some mice - not all - and so this is sometimes and not always) when there is no antibody, there is no keratitis. How does this prove scientists' hypo?
It only mentions that there are mice (can be 4 out of 100) that do not develop antibodies and don't get keratitis. But there can surely be some mice (96) who develop antibodies but don't catch keratitis. Hence, how does D prove scientists' hypo?
I have boldfaced "prove" because I want to ask you do we need to prove that whenever any antibody is formed, keratitis will develop - always?

Because D leaves room for a possibility that 96 mice might develop antibody but still not catch keratitis. Hence not proved. XXXXX

Please help man!! [/quote]

This is a typical strengthen cause and effect problem -

We need to show that only X can lead to the result Y or eliminate any other alternate causes that lead to result Y.

If the cause does not occur then the result does not occur ; Hence , If the cause is there the result is also there.

thanks,
Ankit[/quote]



Thanks Ankit!! This means that we do not need to prove something, as long as we can even mildly support the conclusion. i.e. strengthen doesn't mean to prove something, and that is why as you wrote "to prove that X leads to Y, a statement such as there was no X and there was no Y should suffice."
and so, we should not try to mathematically solve to look out for a possibility (created by our mind) that the statement does not rule out a fact that there was no X, but there was Y - i am trying to break down the statement to find a new possibility that the statement does not deny, but which is not explicitly stated (as I explained this with 96-4 mice example).

I hope I could explain you my thought process. Thanks!![/quote]


you don't need to work your way out of what the argument says - the answers might have something new information but they would totally relate to the argument at hand.

So just keep the below points in mind for Causal type questions :

Causality and Strengthen Question

• Eliminate alternate causes
• Show that when the cause occurs, effect occurs
• Show that when the effect is there, cause has occurred
• Show that reverse is not true
• Show that statistical data behind the cause effect conclusion is correct
• Show that when cause doesn’t occur, effect doesn’t occur

Hope this helps !

Ankit
_________________

You want something, go get it . Period !