If Elvira Johnson agrees to tesitfy against the defendent and the prosecution is able to get a prestigious firm to take their case, then the defendent's changes will be greatly weakened, and he will most likely be given a lengthy sentence.But Charles Chase, a powerful witness for the defense, will onlu cooperate if Elvira Johnson testifies and a prestigious law firm takes the prosecution's case.

Under these circumstances, if the defendent's chances are NOT greatly weakened, then which of the following must be false?

(A) Elvira Johnson testifies against the defendent.
(B) The defendent will get a lengthy sentence.
(C) A prestigious firm will take the prosecution's case.
(D) Charles Chase will cooperate with the defense.
(E) Elvira Johnson might testify againse the defendant.

Please help and explain your explanation.

Thanks

Guest79, this argument is NOT similar to those on the Official GMAT. It is somewhat similar to an LSAT argument, but, to me, not even a good representation of that test.

Basically, the arg is saying that if Elvira AND a prestigious firm get involved, then chances are greatly weakened. Additionally, if Charles Chases is involved, then Elvira and the prestigious firm are involved, and thus the chances are greatly weakened. In essence, if Charles is involved, the defendent's chances are greatly weakened.

Represented in shorthand, we have:

EJ & PF -> Greatly Weakened
Charles Chase -> EF & PF
Charles Chase -> Greatly Weakened

Conversely, the contrapositive of each statement is true

-Greatly Weakened -> -EJ or -PF
-EF or -PF -> -Charles Chase
-Greatly Weakened -> -Charles Chase

Thus, if the defendent's chances are NOT greatly weakened, Charles Chase must NOT have cooperated with the defense.

The correct answer is D.

My advice: Do not think about or discuss this problem again. In fact, you've seen enough of this one! Quickly, hit the little "x" on the top right of your screen and get back to actual GMAT problem types!

Seriously, you would be so much better prepared for the CR section by mastering weaken, strengthen, draw a conclusion, inference, and assumption questions. Don't waste your time with anomalies such as this one.

Hope that helps.
-dan

Oh vow. This was a mind muncher.

Thanks Dan!! I'll make a not of it. Thanks again for taking time to look into this problem.