LSAT Preptest 22//Section 2: LR (1), #13 Flaw question

[Malakai]

Hey guys,

As the title suggests, i'm having trouble understanding choice (c) as being the credited response and why choice (b) is wrong.
To be more particular, I understand how D's (the female) argument first "Presents an additional consideration" - but I don't see how the 2nd part of D's argument "weakens the support given to C's (the male) conclusion by his evidence" actually hurts his argument.
I mistakenly chose (b).

Any feedback would be greatly appreciated!

[timmydoeslsat]

I would not call this a flaw question. I would classify this as a method of reasoning.

How does Darla attack the argument presented?

Charles concludes that air pollution decreases from automobile exhaust.

Darla attacks this idea by introducing a claim of fewer people buying newer cars. And we are told that newer cars tend to pollute the air less than older cars.

So this does weaken Charles' argument as he did not consider other relevant factors of what happens when people are unemployed. Another consideration could have been that people drive more in search of jobs, etc.

Answer choice B is simply way too strong. We do not have support for the idea that these ideas are mutually exclusive. Answer choice B is really an answer choice that is like a unicorn, that one special piece of information that would collapse the argument. The consideration that Darla brings up simply is not strong enough to kill the argument, although it weakens it.