Tough question because of negative structure. IMO: E is correct.
I think the conclusion should be: "Cooking destroys vitamin B1 more than irradiation does" is NOT
correct. So every answer that does not have information regarding the reduction of vitamin B1 is out of scope.
(A) many of the proponents of irradiation are food distributors who gain from food’s having a longer shelf life --> OUT because there is nothing about the reduction of vitamin B1.
(B) it is clear that killing bacteria that may be present on food is not the only effect
that irradiation has --> OUT because the author does not talk about the effect.
(C) cooking is usually the final step in preparing food for consumption, whereas irradiation serves to ensure a longer shelf life for perishable foods --> maybe right, but it just says that cooking is the final step. No information regarding the reduction of vitamin B1 --> OUT
(D) certain kinds of cooking are, in fact, even more destructive of vitamin B1 than carefully controlled irradiation is --> OUT because it is the opposite answer.
(E) for food that is both irradiated and cooked, the reduction of vitamin B1 associated with either process individually is compounded --> CORRECT because it says that for food that is both irradiated and cooked, the reduction of vitamin B1 = the reduction by irradiation + the reduction by cooking, not only by cooking. Hence, the above comparison is not valid.
Please +1 KUDO if my post helps. Thank you.
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