subalpine meadows, nonnative dandelions co-occur with a nati

[vishalwin]

In Colorado subalpine meadows, nonnative dandelions co-occur with a native
flower, the larkspur. Bumblebees visit both species, creating the potential for
interactions between the two species with respect to pollination. In a recent study,
researchers selected 16 plots containing both species; all dandelions were removed
from eight plots; the remaining eight control plots were left undisturbed. The
control plots yielded significantly more larkspur seeds than the dandelion-free
plots, leading the researchers to conclude that the presence of dandelions
facilitates pollination (and hence seed production) in the native species by
attracting more pollinators to the mixed plots.
Which of the following, if true, most seriously undermines the researchers'
reasoning?
(A) Bumblebees preferentially visit dandelions over larkspurs in mixed
plots.
(B) In mixed plots, pollinators can transfer pollen from one species to
another to augment seed production.
(C) If left unchecked, nonnative species like dandelions quickly crowd out
native species.
(D) Seed germination is a more reliable measure of a species' fitness than
seed production.
(E) Soil disturbances can result in fewer blooms, and hence lower seed
production.

[MartyMurray]

We are asked which choice undermines the conclusion. So this is a weaken the conclusion question.

The conclusion here is that the reason for increased seed production is that the presence of dandelions results in increased attraction of pollinators, which in turn do more pollinating than would be done were the number of pollinators not as high.

The basis of this conclusion is an experiment involving removal of dandelions from plots. So what we are looking for is anything that would either conflict with the conclusion made on the basis of that evidence or support a different conclusion.

A) This information is only tangentially related to the argument being discussed and does not conflict with the conclusion or support a different conclusion.

B) This could possibly support a different conclusion. It may be that the dandelions do not attract additional pollinators but rather that they enable the transfer of pollen and thus the augmentation of seed production. So this may be the answer we are looking for.

C) This information on interspecies dynamics does not conflict with the conclusion or offer an alternative explanation.

D) This argument is about seed production rather than seed germination. So this is out of scope.

E) This information supports an alternative conclusion. Given what is said in this answer choice it seems likely that the reason seed production by native species is higher in the mixed plots is simply that the process of removing the dandelions from the other plots disturbed the soil, causing a reduction in blooms and in seed production. Since this information supports a conclusion different from that arrived at by researchers, it undermines their conclusion.

So B or E could work, and really in a way I am not sure that one is better than the other. The game here is to somehow get the right answer though, and so we need a way to find it.

In this case, in the prompt is discussed not simply plots with fewer dandelions but plots from which the dandelions were removed. So I am going to use that as a clue for determining which choice the writer believes to be the best. Removal of dandelions would disturb the soil. So I am going to go with the answer choice that includes discussion of soil disturbances.

The use of a hack like this particular one is not generally necessary for correctly answering official questions, but hacking in general is useful, and so this hack is still illustrative of the types of things one can do to arrive at OA's.

I believe the OA is E.