The correct answer is (B).
(B) Weaken (EXCEPT)
Step 1: Identify the Question Type
The question stem suggests that four answers will weaken the consumer advocate's argument. The correct answer will be the one exception. It will be either a 180 and strengthen the argument, or it will be irrelevant and have no effect on the argument. As always with argument-based questions, start by identifying the conclusion and evidence and then determine the central assumption.
Step 2: Untangle the Stimulus
The advocate mentions that some countries irradiate certain foods to make them last longer. The Contrast Keyword "however" indicates the consumer advocate's point of contention (in this case, the conclusion): people shouldn't eat irradiated foods. What follows is a list of three reasons to avoid such foods: 1) irradiated foods are also exposed to radioactive substances; 2) irradiation can diminish vitamins and leave chemical residues; and 3) irradiation produces harmful radiolytic products.
Step 3: Make a Prediction
Don't let scientific jargon like "irradiated,""gamma rays," and "radiolytic" scare you off. At its core, this is a classic LSAT argument. The author recommends against a course of action (in this case, eating irradiated foods) and backs up the recommendation with a series of negative effects. The assumptions are both that the negatives will directly harm consumers and that the negatives outweigh any benefits. Four answers will weaken the author's conclusion by showing how the listed negatives aren't bad enough to merit a change in consumption. One answer either will strengthen the argument by furthering the dangers attributed to irradiated foods or will be entirely irrelevant.
Step 4: Evaluate the Answer Choices
(B) is irrelevant and, therefore, correct. The author doesn't claim that irradiated food is the only cause of cancer and other health problems. Even if there are many other causes, irradiated foods might still be harmful. Thus, the advocate's argument stands unaffected. That makes this the correct answer.
(A) weakens the argument by showing that unique harmful radiolytic products are rarely found in irradiated food.
(C) weakens the argument by showing that irradiation reduces vitamin content in a miniscule number of fruits and vegetables.
(D) weakens the argument by showing that although radiation can leave behind harmful chemicals, the amount of such chemicals found in irradiated food is actually less than that occurring naturally.
(E) weakens the argument by showing that people who eat irradiated food don't actually get cancer any more often than the general population.
