C，An argument concerning the present-day uses to which historical maps of Native American lands are put=An argument concerning the uses that historical maps of Native American lands are put to uses，讨论印第安地图在现在的用处；native american本土美国人，印第安人
还是要理解句字意思：The sentence, as stands, is confusing. It implies that the 'small cars' are now more fuel efficient than they were in the past. That is the manufactures took an old small car and said, "hey let's make this more efficient." Clearly, however, the small cars today are different from those in the past.we can omit (A), (B).
C gives us a strong reason why reclamation has gotten cheaper. The nature of the mines has changed, making it less difficult to reclaim them.
B looks good EXCEPT look very carefully at the wording of the argument. It says "average cost of a coal mine". Creating fewer coal mines does not matter to this argument, because it is average cost PER mine reclaimed that we are concerned about.
In the time since the reclamation regulations were put in place, the average reclamation cost of a coal mine has gone down, even though there has been no improvement in technology. How can this be?
Possible reason: Even though technology has not improved, some other factor has changed that permits less costly reclamation.
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E，describing a line of reasoning put forth by a researcher and addressing a contention concerning that line of reasoning；描述了某个研究人员的一条推理路线以及解决对该推理路线的争论