A commercial insect trap consists of a small box containing pesticide mixed with glucose, a sweet substance known to attract insect pests. Yet in households where this type of trap has been used regularly for the past several years, recently installed traps are far less effective in eliminating insect pests than were traps of that type installed several years ago. Research scientists have hypothesized that traps in those households decreased in effectiveness because successive generations of the pests developed a resistance to the pesticide in the traps.
Which one of the following, if true, most seriously undermines the hypothesis?
(A) In households where the traps have been used regularly, the proportion of insect pests that have a natural aversion to eating glucose has increased with each successive generation.
(B) Even when only a few individuals out an entire generation of insects survive the effects of a pesticide, the offspring of those individuals are usually resistant to that pesticide.
(C) After eating glucose mixed with the pesticide, insects that live in households that do not use the trap tend to die in greater numbers than do insects from households where the traps have been used regularly.
(D) After the manufacturer of the traps increased the concentration of the pesticide used in the traps, the traps were no more effective in eliminating household insect pests than were the original traps.
(E) The kind of glucose used to bait the traps is one of several different kinds of glucose that occur naturally.

how about D? ...D states another reason for the deficiency of the trap --> the hypothesis may not be the cause.

Is it because this question asks for what undermines the hypothesis (instead of undermine the argument) that we can't choose D?

is it becoz of "natural aversion" that you chose A?!

Btw, is the level of real GMAT questions higher or lower than the level of this question?!! Are the answer choices offered in real GMAT CRs straightforward and distinguishable?

A. Same reason as discussed.

yepp, A

A for me - to weaken an assumption find something else that may have contributed to the state of affairs...

Dont you think in A says reiterates whatever the argument is saying, i.e. successive generations of these pests have infact developed a resistance to this glucose and pesticide mixture. Had the same be said about insects in households which did not use this mixture, then A would have been appropriate.

D clearly gives us another reason why the proportion of pests increased.

(A) In households where the traps have been used regularly, the proportion of insect pests that have a natural aversion to eating glucose has increased with each successive generation.

Definate A for me.

Aversion to eating glucose may cause a drop in the effectiveness of the trap. This weakens the hypothesis that the pesticide is no longer effective.

A makes sense...D deviates a little

Late, but (A). The added glucose shows another reason for the decreased effectiveness. It`s not that the insects are developing a resistance to the pesticide, they just aren`t eating it at all.