Incorrect. The nutritionist never comments on whether it is a waste of money to buy vitamin pills at all. She only says that it is a waste of money to pay for more expensive vitamin pills advertised as having better ingredients.

Incorrect. The nutritionist doesn't assume that vitamin pills containing natural ingredients always cost more than those containing synthesized vitamins. She only states that it is a waste of money to pay more for such pills when they do cost more, which isn't the same thing. Notice that her claim doesn't require any, let alone all, vitamin pills with natural ingredients to actually cost more than vitamin pills with synthesized vitamins. She is just saying that if any of them do, then it is a waste of time to pay additional money for them compared to pills with synthesized vitamins.

Incorrect. This isn't a necessary assumption. If we negate (C) to say that not all brands of vitamin pills contain some synthesized vitamins, that doesn't destroy the nutritionist's argument — it actually fits very well with the notion that some brands of vitamin pills advertise themselves as having more natural ingredients than others.

Incorrect. The nutritionist never says that the claims made by these advertisers are false: it could be true that their ingredients are in fact "higher quality" or "more natural." But she just thinks that's irrelevant to the efficacy of the vitamins themselves, and so thinks it's a waste of money to pay more for such vitamin pills.

Correct. This gets to the assumption we identified in our analysis: even if the vitamin itself is the same, whether it is chemically synthesized or natural, there could be other ingredients in the vitamin pills whose quality is important. If we negate (E) to say that there are some nonvitamin ingredients in vitamin pills whose quality makes one brand worth more money than another brand, then this completely undermines the nutritionist's argument that it is a "waste of money" to pay for vitamin pills with higher quality ingredients.