Hello,

Here's a little insight on what the 'contrapositive' is... it's basic logic which can be disguised pretty well by the GMAT. In particular, I've noticed that many people have problems with passages which state something like the following:

Passage:
Every time John sees a rabbit, John eats a candy bar.

Question: Which of the following is the most supported by the passage?

Choices:
A) Every time John doesn't see a rabbit, John doesn't eat a candy bar.
B) ...
C) ...
D) ...
E) ...

Note that the answer to this problem is not A!!! Rather than thinking about it, wasting precious time, remember the following:

1. If A => B, then B => A doesn't necessarily hold... => means implies.
2. If A => B, then 'not B' => 'not A' *always* holds, because of the contrapositive.

Combining these two statements with the above prompt, A cannot be the answer.

I hope this helped!

Cheers,

D