Human skin gives off an array of gaseous substances, including carbon dioxide and lactic acid, both of which attract ...

Emily on August 24, 2018

Answer Choice Face Off

Why answer choice B instead of E for this question? Thank you!

4 Replies

Mehran on August 25, 2018

Hi @EmilyMarieMenendez,thanks for your post.

Start with the stimulus. This one presents an argument. The conclusion is "some other gaseous substance given off by human skin also attracts mosquitoes." Why? The support for this conclusion is that neither carbon dioxide nor lactic acid - "whether alone or combined with one another" - will attract mosquitoes as much as a bare human arm will, even in complete darkness.

OK. First, notice that this eliminates the mosquitoes' sight as a possible cause. But the argument concludes that it must be a "gaseous substance given off by human skin" that attracts the mosquitoes, without eliminating other possible causes.

The question stem is a Strengthen with Necessary Premise question. The argument assumes there is no cause other than gaseous substances attracting the mosquitoes. Answer choice (B) articulates this assumption (providing "body heat" as an alternative source of the attraction for the mosquitoes).

Remember that negating the right answer on a Strengthen with Necessary Premise question will make the argument in the stimulus fall apart. What is the negation of answer choice (B)? "Mosquitoes are attracted to humans by body heat." If you added this to the stimulus, the argument in the stimulus would fall apart. That's how you know you have the right answer.

Hope this helps. Please let us know if you have any additional questions.

Emily on August 25, 2018

Okay, I understand this better now. The Strengthen with Necessary is the lesson example about the great basketball player, with arms being necessary to play basketball well yea?

Can you please break down how the argument in the stimulus would fall apart for the mosquito argument?

Thank you so much!

on June 14 at 09:03AM

the arguement falls apart for both B and E. if human skin emits gas that repels mosquitoes, the the conclusion that it emits gas that attracts mosquitoes falls apart. MORE so than if mosquitoes are attracted to body heat. surely they can be attracted to body heat AND be attracted to another gaseous emission from human skin.

For (B) if human skin sometimes emits repellent, then even if it did emit an attractive gas, the mosquitoes would be less likely to be attracted to the arm.

on June 14 at 09:04AM

so yes, please explain further. the only reason I got this is because I am starting to undertsand the answers the LSAT wants even if I disagree with it