NextStep FL 4 B/BC #20

[jeep1010]

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The answer explanation says:

A is correct. The charcoal filter in this experiment was used to eliminate all odors and contaminants in this experiment except for the odor to which the scientists are intentionally exposing the mice. The humidifier is likely being used to simulate realistic environmental conditions, as well as to provide moisture droplets to which the odor-causing particulates cling.

The only thing that the passage mentions about Charcoal Filter and Humidified Air is:

A group of researchers was interested in exploring the involvement of olfactory bulb mitral cells in the adaptation response. Scientists anesthetized 11 mice, exposed the skull, drilled over each of the lateral olfactory tracts, and attached them to recording electrodes. Odorants were directed through a carrier stream of charcoal-filtered, humidified air (1 L/minute), resulting in a final odorant vapor-phase partial pressure of 5 Pa. Pre-adaptation recordings of olfactory bulb mitral cell activity were collected. The mice were then exposed to several protocols
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I have been trying to figure out how I would deduce that the charcoal filter is used to eliminate all odors and contaminants and the humidifier is used to stimulate realistic environment. Is this something that we should know as background knowledge?

@NextStepTutor_2 @NextStepTutor_3

 

[aldol16]

Well, you should be able to deduce that the point of filtering the air in the first place is to remove all the stuff that you don't want in it. And humidified means just that - to add moisture to the air, which you could deduce to be relevant to the simulation in some manner.

 

[NextStepTutor_3]

Yes, that's exactly right. You certainly don't need to have any background knowledge about the purpose of a humidifier or a charcoal filter, but we can use our reasoning, just as @aldol16 said.

We can also use process of elimination, which is enormously helpful on the MCAT in general. We can eliminate choice B, because the passage never said we wanted the mice to smell the odor of charcoal - just that odorants were being presented to the mice in a stream of air that had been charcoal-filtered. We can assume that the mice are supposed to smell the odorants, not the charcoal (after all, it would be a bad filter that made our air more contaminated).

We can eliminate choice C, because the lack of a humidifier would make the air too dry, not too humid.

And we can eliminate choice D, first because we have no way of knowing how a filter and humidifier would "maintain the health of the mice," and also because even if they did somehow keep the mice healthy, that wouldn't be a reason why the data "could still be used." On the contrary, if our mice suddenly became unhealthy due to the lack of a humidifier and filter, we probably wouldn't want to use those data as their lack of health may serve as a confounding factor.