Which of the following most logically completes the argument? The irradiation of food kills bacteria and thus retards（减缓） spoilage. However, it also lowers the nutritional value of many foods. For example, irradiation destroys a significant percentage of whatever vitamin B1 a food may contain. Proponents of irradiation point out that irradiation is no worse in this respect than cooking. However, this fact is either beside the point, since much irradiated food is eaten raw, or else misleading, since _______
- many of the proponents of irradiation are food distributors who gain from food’s having a longer shelf life
- it is clear that killing bacteria that may be present on food is not the only effect that irradiation has
- cooking is usually the final step in preparing food for consumption, whereas irradiation serves to ensure a longer shelf life for perishable foods
- certain kinds of cooking are, in fact, even more destructive of vitamin B1 than carefully controlled irradiation is
- for food that is both irradiated and cooked, the reduction of vitamin B1 associated with either process individually is compounded
请帮我解释一下意思,另外这类题通常怎么做,谢谢 | 
