Powerscore CR Bible --> Chapter 10: MOR & FIR (First/Prove Family)

Hi all,

I have just completed the Powerscore CR Bible and found it too good.
But I found Chapter 10 to be somewhat confusing. I need an answer to this post only from people who have read powerscore CR Bible.

Till the time I read the theory part of common errors of reasoning, It was still fine. But when I solved the 'Identify the flaw in the Argument Drill' I felt that I can classify the argument into one or more categories of common errors of reasoning.

A classic example of this confusion is Ques #1 on Page 303 that lies under Parallel Reasoning as MOR (Method of reasoning) is one of the elements that has to be matched while choosing the correct answer.

When I solved this Ques. I marked the error of reasoning as : Some evidence against a position is taken to prove that the position is false.
And marked answer accordingly.

But when I read the Answer's explanation, the author has used 'Source of Argument' error and the one error mentioned above in tandem. And finally author marked the answer according to 'Source of Argument' error.

I want to know that how could I be dead sure that only this error of reasoning is possible?
Because as I already wrote above I am able to classify the error of reasoning into one or more categories.

(OR) Am I the only person who is getting confused with these errors of reasoning mentioned in chapter 10?