Hi blade21cn and desiboy96!
blade21cn: If you can't discriminate between scientifically valid and invalid information, the likelihood of you somehow always guessing right and only using scientifically valid information in your decision-making would be very low. Technically possible? Sure. But I would say you can consider these concepts functionally equivalent here, especially when considering all of your answer choice possibilities. And it's always good to look for premises that aren't directly tied to conclusions, but there will often be premises that don't end up playing a big role in the argument or in answering the question, so it's not a major cause for concern. As for your last question, answer choice (B) just connects the premise to the conclusion. It doesn't have to be specific to web research. If people who use the web to diagnose themselves cannot differentiate between valid and invalid information, and people who don't rely only on valid information to make their decisions are likely to do more harm then good, then people who use the web to diagnose themselves are likely to do more harm than good.
desiboy96: Not quite. You're the right that you should be careful to not choose an answer choice in an Assumption question that provides more than what is basically necessary. But answer choice (E) has much bigger problems with the conditional reasoning than with the comparison between the "will" and the "likely."
As Steve said earlier in the thread:
Answer E says that the only way people can possibly harm themselves is by relying on quackery--there's no other way anyone could ever harm themselves. This is a much more broad assumption than required by the author’s argument, so it cannot be the right answer choice.
And check out Nikki's explanation of how to negate (E) for the Assumption Negation Technique:
Answer choice (E) contains a conditional statement, which can be diagrammed as follows:
Do more harm than good Rely on quackery instead of valid info
To logically negate this answer choice, you need to show that the sufficient condition can occur even in the absence of the necessary condition. In other words, the logical opposite of answer choice (E) would state,
People can do themselves more harm than good even if they don't rely on quackery to diagnose their medical conditions.
In other words, you can harm yourself even if you use scientifically valid information. Nobody said that relying on scientifically valid information precludes the possibility of harm, which is why the logical opposite of answer choice (E) has no bearing on the conclusion of the argument.
Hope this helps!
Best,
Kelsey