Mammals cannot digest cellulose and therefore cannot directly

Question

Mammals cannot digest cellulose and therefore cannot directly obtain glucose from wood. Mushrooms can, however; and some mushrooms use cellulose to make highly branched polymers, the branches of which are a form of glucose called beta-glucans. Beta-glucan extracts from various types of mushrooms slow, reverse, or prevent the growth of cancerous tumors in mammals, and the antitumor activity of beta-glucans increases as the degree of branching increases. These extracts prevent tumor growth not by killing cancer cells directly but by increasing immune-cell activity. 
Which one of the following is most strongly supported by the information above?

(A) Mammals obtain no beneficial health effects from eating cellulose.

(B) If extracts from a type of mushroom slow, reverse, or prevent the growth of cancerous tumors in mammals, then the mushroom is capable of using cellulose to make beta-glucans.

(C) The greater the degree of branching of beta-glucans, the greater the degree of immune-cell activity it triggers in mammals.

(D) Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells.

(E) Any organism capable of obtaining glucose from wood can use cellulose to make beta-glucans.

Source: LSAT

KarishmaB · Accepted Answer

- Some mushrooms use cellulose to make highly branched polymers, the branches of which are a form of glucose called beta-glucans. 
- Beta-glucan extracts from various types of mushrooms slow, reverse, or prevent the growth of cancerous tumors in mammals
- The antitumor activity of beta-glucans increases as the degree of branching increases. 
- These extracts prevent tumor growth NOT by killing cancer cells directly BUT BY increasing immune-cell activity.

The premises tell us that the antitumor activity increases as degree of branching increases. They also tell us that antitumour activity is "increasing immune-cell activity". So we can deduce that degree of immune cell activity increases as degree of branching increases. 
This is option (C) and is correct.

(D) Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells.

Not correct. In fact, it seems that immune cell activity does prevent tutor growth. Beta gluten increases immune-cell activity leading to preventing tutor growth. So it seems that increased immune cell activity does in fact prevent tumour growth.

tanvi9 · Answer

C : correct answer 
as it is a must be true question, word by word this only holds true,
but it took me some time to solve.

akela · Answer

(A) Argument says nothing about beneficial health effects: "Mammals cannot digest cellulose and obtain glucose from wood." There might be other beneficial health effects, we do not know
(B) Reverses reasoning in the argument
Argument: "If mushrooms can convert cellulose into beta-glucans -> prevent tumors
Answer choice: prevent tumors > capable of using cellulose to make beta-glucans. 
(C) Contender as it is well supported in the stimulus:"antitumor activity of beta-glucans increases as the degree of branching increases"
(D) Stimulus: " These extracts  prevent tumor growth not by killing cancer cells". We know don't know how immune-cell activity prevents tumor growth. Shell game?
(E) too broad. we are talking about mushrooms

nightblade354 · Answer

LSAT question, bumping for discussion!

abhishek31 · Answer

Hi, I was able to narrow down to Option C & D, but eventually ended up choosing option D. Can you please suggest me why D is a poor choice over C?

Aviral1995 · Answer

VeritasKarishma   egmat  i have a doubt with option D 
Question says- - These extracts prevent tumor growth NOT by killing cancer cells directly BUT BY increasing immune-cell activity.
In option D -Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells.
It means Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells but by any other means(increasing immunity).
I think in the answer given it is interpreted only Immune-cell activity in mammals does not prevent tumor growth which is wrong as per the question but when we consider full statement- Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells. we get a different inference
Please let me know, if i am missing something VeritasKarishma

KarishmaB · Answer

This is what the argument tells us:
These extracts prevent tumor growth not by killing cancer cells directly but by increasing immune-cell activity.

It says that the extracts from mushrooms do not kill cancer cells directly. The extracts increase immune cell activity of mammals i.e. they make the mammals own immune system more active so that it fights cancer cells better.

Now we need something that is supported by the argument i.e. something which has no new info.

(D) Immune-cell activity in mammals does not prevent tumor growth by killing cancer cells.
How does immune cell activity prevent tumour growth, we don't know. From the argument, we just know that increased immune cell activity leads to prevention of tumour growth. Now do the immune cells kill cancer cells or do they create a protective cover around them so that they hibernate or whatever, we don't know. So we CANNOT say from the argument that immune cell activity does not prevent tumour growth by killing cancer cells - it may or may not. We don't have enough data to figure this out.

Diya52 · Answer

Can someone please explain why B is wrong?

Tea12 · Answer

Choice B says "(B) If extracts from a type of mushroom slow, reverse, or prevent the growth of cancerous tumors in mammals, then the mushroom is capable of using cellulose to make beta-glucans." 
 The argument says that beta glucans from mushrooms lead to reduction of cancer by enhancing immunity cells, but we cannot apply the reverse chronology as is said in B. 
For ex - If argument is saying , X leads to y. So we cannot infer from the argument that Y leads to X , this is what choice B is doing.

VerbalBot · Answer

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Mammals cannot digest cellulose and therefore cannot directly

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Mammals cannot digest cellulose and therefore cannot directly

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