Actually, check the premise ( mention a new reason) and conclusion( the two reasons is incompleted) ,you want to make the conclusion reasonable and then you need a assumption that :the new reason is a reason for the phenomenon.
Conclusion: Thus, the (scarcity) of food is not merely a function of limited resources and population growth.
Premise: that much of the world’s agricultural resources are used to feed livestock instead of people. ( eg: In U.S, 1/2 the agricultural acreage -> Livestock. A steer consume 21 pounds gain, produing 1 pound meat)
Asking: Assumption to make the conclusion reasonable.
D.Growing crops for human consumption of the acreage (currently devoted to crops for livestock)will yield more food for more people. Saying: Growing corps devoted to livestock is a reason for the scarcity of food, that is , other two reasons mentioned are not the whole .
Is it complicated, isn't ? How to quickly fix the question?
9. Free public education is the best form of education there is. Therefore, we must fight to ensure its continued existence; that is, we must be ready to defend the principle of equality of educational opportunity. Because this principle is well worth defending, it is clear that free public education is better than any other form of education.
Which one of the following illustrates the same weak reasoning as found in the passage?
(A) I love music, and that’s why I listen to it constantly. I have my stereo or radio on every waking minute. Since I play music all the time, I must really love it.
(B) Books are my most valuable possessions. My books are like my friends—each pleases me in different ways. Just as I would give up everything to save my friends, so too with my books.
(C) I would much rather be poor and respected than be rich and despised. To have the respect of others is far more valuable than to have millions of dollars.
(D) I have never been betrayed by any of my friends. They have been true to me through good times and bad. Therefore I will never betray any of my friends.
(E) Because every plant I have ever seen has green leaves, I have concluded that all plants must have green leaves. This looks like a plant but it does not have green leaves, so it cannot be a plant.
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这一题是lsat中常见的逻辑相似题，这种题型比较简单，只要弄清楚原文的论证过程即可，无需对结论，前提产生过多联想。
原文中的论证顺序就是因为A，所以B；又因为B，所以A。（循环论证）
符合这种双重因果论证的只有a.
b,d一层因果关系，c,无因果，e,因为A，所以B；又因为非B，所以非A
