To clarify about the "question 2" you're referring to, is it the one that states, "If Max were guilty, he would not ask the police to investigate. Therefore, his asking the police to investigate shows that he is not guilty."
Is this the one? I'm assuming it is. If it isn't let me know and I'll happily go over the #2 you were actually referring to as well. For now, let's look at this one.
The stimulus says, "If Max were guilty, he would not ask the police to investigate. Therefore, his asking the police to investigate shows that he is not guilty."
The structure of the stimulus is
G - >/API API - >/G
P: API C: /G
This is a valid contrapositive argument structure. It's invoking the sufficient condition of the contrapositive to conclude the necessary condition of the contrapositive.
The question asks, "The logical structure of the argument above is most similar to which one of the following?"
The reason that Mehran didn't show the contrapositive on (E) is because we could already tell the argument structure without doing the contrapositive.
(E) says, "If Sally were sociable, she would not avoid her friends. Therefore, the fact that she is sociable shows that she does not avoid her friends."
(E) can be diagrammed as
S - >/AF P:S C: /AF
If we did the contrapositive for (E), we'd have
S - >/AF AF - >/S
P:S C: /AF
We still see that (E) has a valid positive argument structure that does not use the contrapositive of the argument. As such, we know that the structure does not match what we found in the stimulus.
In short, the reason Mehran didn't show the contrapositive for (E) is that we can see that it's a valid positive argument structure without doing the contrapositive. That said, if it helps you to always do the contrapositive of each conditional statement, then it's fine for you to do that while you're working on problems.
Does this make sense? Let us know if you have any more questions!
