Susan's conclusion: The testing of ordinary consumer products on animals is justifiable.
Susan's evidence: Testing on animals is justifiable if it can lead to cures for human ailments. Cleanliness, convenience, and beauty are worthwhile human values deserving of support.
Susan's assumption: Using animals to test ordinary consumer products, which promote cleanliness, etc., can lead to cures for human ailments.

That assumption above is the flaw in Susan's argument. She says that animal testing of ordinary consumer products is justifiable ON THE SAME GROUNDS as other kinds of experimentation that can lead preserve human life. That's a big, unwarranted leap. Cleanliness is a human value -- OK. But there's no reason to think that all human values lead to cures that preserve human life. This is what Choice E, the correct choice, says.

Choice A: There's no contradiction between saying that animal testing is justifiable if it supports human values and also saying that animal testing is justifiable only if it leads to cures. It's only when human values are specified to include things like cleanliness and beauty that the argument runs into trouble.
Choice B: This is simply incorrect. She never rates human cleanliness, etc. relative to the preservation of animal life.
Choice C: Susan uses the word "value" twice. In the first sentence, she uses it as a verb and in her second sentence as a noun. There is no flaw implied in her use of the word this way. As with Choice A, it's only when human values are specified to include things like cleanliness and beauty that the argument runs into trouble.
Choice D: Susan never makes such a broad claim. She only refers to certain consumer products.

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