The argument concludes that: "A similar fate is likely to befall modern civilizations that continue to rely heavily on irrigation for agriculture."
Why? We know that for 2,000 years the ancient Sumerians depended on irrigation to sustain the agriculture that fed their civilization. But, we are told that at some point, irrigation built up in the soil toxic levels of the salts and other impurities left behind when water evaporates. The Sumerian civilization collapsed when its soil became unable to support agriculture.
The archaeologist is assuming that modern irrigation will have the same problem as Sumerian irrigation, i.e. that the irrigation will build up toxic levels of salts and other impurities in the soil. But, what if modern irrigation has fixed this issue?
This is exactly what answer choice (C) points out: "Many modern farmers use irrigation techniques that avoid the buildup of salts and other toxic impurities in the soul."
Thus, it is not necessarily true that modern irrigation will have the same issue and negative effects as Sumerian irrigation.
Hope that was helpful! Please let us know if you have any other questions.
cjahangiriDecember 27, 2019
This makes sense, but could you please explain why C is a better answer choice than D?
July 26, 2020
C is better because the argument is about modern farmers who rely on irrigation and D all though it gives a reason for why the civilization would not fall ( by avoiding irrigation all together ) it doesn't weaken the argument. C weakens the argument by saying that the techniques used in modern irrigation will not bring the same result of toxins so it shouldn't bring the same result of the civilization falling.
