Hi @maos2910, thanks for your post. This is a Strengthen with Necessary Premise question ("is an assumption the argument requires"). Let's first examine the stimulus carefully.
The stimulus presents an argument, which proceeds as follows: P: People who browse the web for medical info often cannot discriminate between scientifically valid info and quackery. P: Much of the quackery is particularly appealing to readers with no medical background because it is usually written more clearly than scientific papers. C: Thus, people who rely on the web when attempting to diagnose their medical conditions are likely to do themselves more harm than good.
Notice the leap from the premises to the conclusion. The premises talk about quackery, but do not mention harm. Yet the conclusion is that people who rely on the web will be harmed by quackery.
We need to bridge this gap in the argument. Answer choice (B) identifies the missing, necessary assumption: People who attempt to diagnose their medical conditions are likely to do themselves more ham than good, unless they rely exclusively on scientifically valid information.
Answer choice (E) can be eliminated because the argument in the stimulus does not require the assumption that *only* quackery can cause more harm than good.
Hope this helps! Please let us know if you have any additional questions!
