Agricultural economist: We can increase agricultural production without reducing biodiversity, but only if we abandon conventional agriculture. Thus, if we choose to sustain economic growth, which requires increasing agricultural production, we should radically modify agricultural techniques.
Which one of the following principles, if valid, most helps to justify the agricultural economist's reasoning?
A) Agricultural production should be reduced if doing so would increase biodiveristy
B) Economic growth should not be pursued at the expense of a loss of biodiveristy
C) Economic growth should be sustained only as long as agricultural production continues to increase
D) Preserving biodiveristy is no more important than increasing agricultural production
E) Agricultural techniques should be radically modified only if doing so would further the extent to which we can increase agricultural production.
D？
What is the key?
楼上兄弟，又碰到了。呵呵
这道题我选C。
前提 abandon conventional agriculture=radically modify agricultural techniques,是一个东西。你可以说不是，但那是assumption题。without reducing biodiversity和题设无关，是干扰。
逻辑分析
1。increase agricultural production-> abandon conventional agriculture
2。increase agricultural production is NECESSARY BUT NOT SUFFICIENT to sustain economic growth,
结论
3。 sustain economic growth->radically modify agricultural techniques
从这里可以看出，要推出结论，这里面有个GAP，就是2里面所说的，"require" is only necessary but not sufficient。所以，要补上这个GAP，就需要，
sustain economic growth->increase agricultural production
而这正是C里面所说的。
我认为应该选B。
hehe, sensornet兄讲的有理！
兄弟我看到C时，as long as的意思没翻译对，所以还以为是无关项
这道题是道没有正确答案的讨论题. 但看了别的论坛上的讨论,都同意B.我仔细考虑一下觉得B应该是正确答案.
cause: abandon conventional agriculture ------> increase agricultural production without reducing biodiversity
reasoning: should radically modify agricultural techniques ------> increase agricultural production ,---> sustain economic growth
increase agricultural production 可以有很多方法,为什么should modify agricultural techniques? 因为前面原因中已经提到,only if we abandon conventional agriculture 才可以increase without reducing biodiversity.
the reasoning 其实默认了 sustain economic growth 要考虑保持diversity.
所以应该选 B) Economic growth should not be pursued at the expense of a loss of biodiveristy
不知道我有没有说清楚．
hi, sensornet,glad to see you again. 这道题我还是从那个论坛上找到的．
A only if B 的逻辑关系是 A->B,
A if B 的逻辑关系是 B->A。
所以你看你的cause里面的逻辑关系，好像是反了。所以你的结论可能不对。
请看下面的链接。我做这道题的时侯就觉得跟那道题很象。
http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=17359&page=1
个人观点是B，不过解释跟9楼有所不同，赞同楼上给出的逻辑关系。
A. 本文只给了个前提条件increase agricultural production without reducing biodiversity, 这里reduce production和increase biodiversity的关系如何，跟本文推论应该是无太大关系.
B.由economic growth, which requires increasing agricultural production(A require B等价A→B),这样economic growth→increasing agricultural production
把B取反，Economic growth should be pursued at the expense of a loss of biodiveristy，换句话at the expense of a loss of biodiveristy是Economic growth的必要条件：economic growth→at the expense of a loss of biodiveristy，这样结合上面的推论就会有increasing agricultural production at the expense of a loss of biodiveristy这和推论的前提条件increase agricultural production without reducing biodiversity矛盾，所以B helps to justify the agricultural economist's reasoning
C.几乎是文中economic growth, which requires increasing agricultural production的等价说法，对文中的reasoning不起额外的作用。
D.important无关
E.extent无关
BTW, 这种题涉及充分必要条件，现在Gmat中较少涉及。个人觉得甚至不知道也没关系。
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