LR Question 24 Explanation
QUESTION TEXT: Mammals cannot digest cellulose and therefore cannot…
QUESTION TYPE: Most Strongly Supported
FACTS:
- Mushrooms can make make glucose from wood.
- Some mushrooms makes branched polymers, with beta-glucans at the ends.
- Beta glucans block cancer, by increasing immune system activity.
- The more beta glucans branch, the more they stop tumors.
ANALYSIS: I rearranged facts three and four to make things slightly clearer. Though this is a most strongly supported question, you could actually draw this. Note that this is a directional drawing, to show the direction of the cause-effect relationship. It’s not an “if-then” diagram:
branching ↑ ➞ immune system ↑ ➞ tumors ↓
So more branching in beta glucans leads to more immune activity, which reduces tumors.
___________
- Not so. The stimulus said we can’t digest cellulose, but it’s possible we get some other benefit.
- This is an incorrect reversal. We know that beta glucans reduce cancer. But that doesn’t mean that only beta glucans reduce cancer.
- CORRECT. See the analysis above. We know that more branching leads to more anti-tumor effects. And beta glucans fight tumors by activating the immune system.
So, that means that branching increases tumor-fighting by increasing immune system activity. - There’s no support for this. The stimulus said that beta-glucans prevent tumor growth by stimulating the immune system. So it seems likely that the immune system does kill tumor cells.
- There’s no support for this. We know that mushrooms can make beta-glucans, and that they do so by getting glucose from wood. But that doesn’t mean that anything that gets glucose from wood can make beta glucans.
More Resources for Most Strongly Supported Questions
- Intro Course lesson: This intro course lesson covers Most Strongly Supported questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers most strongly supported questions.
I still don’t understand how A can’t be correct. If mammals can’t digest cellulose than how on earth can they obtain beneficial health benefits from eating cellulose? Seemed like a common sense answer. Are there things out there that we can’t digest but that are beneficial to eat??
There are vegetables like corn and celery that contain a lot of cellulose that we typically can’t digest, yet would still be beneficial to eat. Same goes for a lot of seeds. “No beneficial health effects” is a very strong (and unsupported) inference from “cannot digest.”
Another thing to keep in mind here is that A only responds to the first sentence of the stimulus. It completely ignores the rest of the stimulus, which outlines a whole chain of events that is much more likely to draw an inference from. A good tip for MSS/MBT/MBF questions is to see what path they’re leading you down.
Hope that helps! Let me know if you have further questions.