Q5 - Only some strains of the

[dj_grey]

I have read the question and answers over and over.

My selection as the best answer are
(a), (b), and (e).

I have eliminated (c) and (d)

Could you tell me what is the right answer and why?

[bbirdwell]

Here's what we know:
1. some plants are naturally resistant, getting infected without become diseased
2. when they get infected, their acid rises; the acid in non-resistant plants does not rise
3. second experiment: non-resistant plants injected with acid and exposed to virus did not become diseased

Obvious inference? Acid plays a role in resisting the disease.

Note the distinction between infection and disease.

(A) We have no evidence to support this, as there is no mention of diseased plants being injected. Only infected ones.

(B) Bingo. Note the phrase "at least." Very appealing on inference questions, as it's easier to prove that something plays "at least some part" than it is to prove that something "always causes something else to happen."

(C) We actually have evidence to contradict this. The acid is naturally occurring in the plants -- the resistant strains increase theirs by 500% when infected, the non-resistant strains do not.

(D) This could be true, however we have no evidence to support it. No facts are given regarding the level of acid in uninfected plants - only that the level rises in some infected plants.

(E) We don't know whether the production of the acid can be increased. In the experiment, the acid was injected, not produced by the plants.

Does that help? Lemme know!

[nflamel69]

I also want to add one point. in choice (E), it infers the production of the acid is the cause of the resistance to the virus, but the argument only offered a correlation, no causation is discussed

[nthakka]

(C) REALLY tripped me up. I jumped on "nonresistent plants injected with salicyclic acid" If they are being injected with it, can't we infer they did not originally possess this acid? I know they can simply raise their levels, but with the way it's worded in the stimulus it does not seem to indicate that.

Very weirdly worded AC, C is.

I can definitely see why B is correct though. Increasing 5fold is significant for the plants that were naturally resistant. And you can infer it plays a role in how it resists the disease.

[Slymobius]

(C) REALLY tripped me up. I jumped on "nonresistent plants injected with salicyclic acid" If they are being injected with it, can't we infer they did not originally possess this acid? I know they can simply raise their levels, but with the way it's worded in the stimulus it does not seem to indicate that.

Very weirdly worded AC, C is.

I can definitely see why B is correct though. Increasing 5fold is significant for the plants that were naturally resistant. And you can infer it plays a role in how it resists the disease.

No we can't. In fact, we KNOW that they already do as lines 4-7 say "levels of naturally occurring salicyic acid in these plants increased fivefold; no such increase occurred in the nonresistant plants"

It's naturally occurring in the tobacco plants. The nonresistant plants simply don't have the trigger (whatever that may be) to increase their acid levels fivefold like the resistant plants do. Thus, it's implied that there is at least small amount of acid in the nonresistant plants, but not enough to fight the infection.

[sclw64]

For the choice E, it really confuses me because I think the "certain strains" of tobacco plants can refer to the resistant strains, and then the choice E makes sense.