An important thing to observe here is the usage of “each other” and “one another”. These expressions are used to show reciprocal actions. Take these simple examples:
a. Laurel and Hardy love each other.
This sentence means that Laurel loves Hardy. And Hardy loves Laurel. So here we have reciprocal action here.
b. All the cartoon characters start fighting with one another towards the end of the show.
This sentence means that one cartoon character was fighting with every other character. Here to the action is reciprocal.
However, the original meaning of the sentence does not intend to express reciprocal actions. It actually compares all the producing firms with one another. On this basis, choices A and C can be eliminated for incorrect use of “each other” and “one another”.
"to ___" —> same timeframe as the larger sentence/context in which it appears
"to have ___ed" —> earlier than the timeframe of the larger sentence/context
E.g.,
You appear to be injured. (It seems that you're injured right now.)
vs.
You appear to have been injured at work. (You may still be hurt; you may be OK now. The injury happened earlier.)
The Neanderthals don't exist anymore—and the main sentence is in the present (it's about what appears to be the case NOW)—so we definitely need "to have ___".
e- Insects that develop a tolerance for feeding on a plant that had previously been toxic to them, and the resultant changes within that plant species，feeding on a plant that had previously been toxic to them= "antiherbivore chemistry"
a选项- problem指“不同的企业受到环境法规的影响不同”，但是看下半句，作者并没有就解决这个问题给出办法，即如何解决受到环境法规影响不同；作者基于承认这个问题存在的基础上，就如何应对环境法规给出建议，因此suggest possible solutions（to this problem）不正确，文中没有提及
e选项-文中第一句”所有企业收到影响相同“，下一句”实际上企业收到的影响不同“，并给出三点理由（For example, additionally，moreover，）
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我老是喜欢加入自己的常识认知。。。