Hi MB,
You got it! Answer choice (E) is correct precisely because if the fossilized life forms in real amber look awkward or grotesque, then pieces that contain normal-appearing insects are even MORE likely to be fake.
I must caution you against approaching these questions by virtue of keyword-matching. For instance, there is no need to "tie" the notion of "normal-appearing" insects in the conclusion to the rest of the argument - the premises already establish that foragers can trick you by inserting normal-appearing insects into the amber, which is why the appearance of such insects should be a cause for concern. The issue with the conclusion is one involving probability: how do we know for sure that amber is
more likely to be fake if it contains normal-appearing insects?
Let's try a little hypothetical: What if all amber - fake or not - contained normal-appearing insects? After all, we know that valuable amber contains fossilized life forms (first sentence). What if 99% of all amber sold is valuable and real, all of it containing normal appearing insects? Then, even if every piece of fake amber contains a similar insect, that would only account for 1% of all the amber being sold. So, if you received a piece containing normal-appearing insects, is that piece more likely to be fake than real? Of course it's probably real
Do you see the flaw in the argument?
If answer choice (E) is true, the probabilistic error in reasoning is swiftly removed. We now know that real amber usually contains not normal appearing insects, but rather insects that look tortured and awkward.
So, if you come across a piece of amber whose insect looks like it passed away peacefully in its sleep, there is probably something fishy going on!
Hope this clears it up!
Thanks,