## How to approach #21 on PT45

Prepare for the LSAT or discuss it with others in this forum.
skippy1

Posts: 96
Joined: Tue Aug 10, 2010 1:56 am

### How to approach #21 on PT45

I left this question for the end but still didn't get it right.

Would someone please explain the step by step approach to this question? I was able to narrow it down to A,B,D but then I got really confused under time pressure.

Thanks!

Jeffort

Posts: 1888
Joined: Wed Jun 18, 2008 4:43 pm

### Re: How to approach #21 on PT45

It would be helpful to know which section you are asking about, all of them have a question #21.

skippy1

Posts: 96
Joined: Tue Aug 10, 2010 1:56 am

### Re: How to approach #21 on PT45

oops! Sorry - Section 1 - LR, #21. Thanks!

cmaas

Posts: 121
Joined: Sat Aug 28, 2010 9:33 pm

### Re: How to approach #21 on PT45

I just took this test today. The stimulus makes the conclusion that there is no consistent causal link between meteor impact and extinction. This is supported by the fact that there have been documented meteor impacts without extinction and extinctions without meteor impact. The question asks which answer choice allows the conclusion to be drawn. Answer choice (A) basically says CCL ---> (MI ---> Ex). This also means ~(MI ----> Ex) ---> ~CCL. CCL is consistent causal link. MI is meteor impact. Ex is extinction. Because we know that ~(MI ----> Ex) then the conclusion that there is no consistent causal link would be true, if this premise (answer choice) is assumed.

lakers3peat

Posts: 464
Joined: Thu Sep 16, 2010 7:10 pm

### Re: How to approach #21 on PT45

Sorry to necro this thread, but I had a little difficulty wrapping my finger around this one--- was debating between A and D---ultimately, chose A out of dumb luck. Now in review, I am trying to rationalize why this is the correct answer and have looked through the old forum posts when I came across this.

To my dissatisfaction, I found the above poster's explanation to be a little convoluted to me and the diagramming to be unnecessary. The diagramming has me more confused then I was originally actually so I challenge somone out there to answer this for me!!!!!! Test your knowledge: What is the better way of explaining this?

If you are new to the thread, this question is about mass extinction, meteor impacts, and a consistent causaul link.

Evidence shows some meteor impacts have been followed by mass extinctions but evidence shows some meteor impacts have not been followed by mass extinctions.
Thus record shows no "consistent causal link" between the two events.

the correct answer(A) comes in the form of a conditional statement that says, IF there were a consistent link, then all meteor impacts would be followed by mass extinctions. Is this correct because it basically defines what qualifies a "consistent casual link."
IF there were a consistent link, then all occurrences would have to be this way(meteor impact ---> mass extinction).

Since the premises in the stimulus indicate that it doesn't always occur this way, the conclusion that there is no consistent casual link is qualified by the conditional in the answer choice?

Also if someone could explain to me what the difference is between the first sentence(records show meteor impacts precede mass extinctions, many extinctions did not follow meteor impacts) and the second(likewise, there are many records of meteor impacts that do not seem to follow mass extinction) that would be GREATLY GREATLY appreciated. I don't know if I'm missing something or just not reading it properly but it seems like the second statement is just a restatement of the first premise, in different words.