貌似想通了PREP1-13，分享给大家

shufenliu

照着Ron的理论，我写了一个类比的例子，感觉好理解多了。
c) as long as John can make a lot of money, he can afford an iphone, since he can spend his income as much as he wish.
e) as long as John can make a lot of money, he can afford an iphone, since currently he is very poor.
John 是不是能买起iphone， 和他现在穷不穷没有关系，而和他能花多少钱有关系。（如果John挣到的钱都必须寄到老家，那么挣再多多钱也买不到新手机）
在这里，把“as long as John can make a lot of money“类比为”government successfully increases the demand of solar power“, 把”he can spend his income as much as he wish“类比为 ” US manufacturers have competitive advantages in the US", "can afford an iphone" 类比为 “maintain production". 就会发现，美国的manufacturers 能不能成功和现在的美国市场有多小，没有关系，而是和他们在本国抢占市场的能力有关系。

yaguohple

我觉得C选项略为牵强。
如果美国市场对于这个东西的需求不大的话。不管相较于竞争对手是否有优势，都是不会生产很多产品的。打个比方，美国人只需要100台，如果有竞争的话，可能美国本土企业只生产60台，没有竞争就生产100台。但是一旦增加了消费需求的话，就可能是10000台了。所以感觉消费需求才是带动增长的关键点。
而且此题的conclusion的premise据我看来应该是if increase the demand. 那这样的话E答案更为合理一些，因为市场需求小，所以要刺激市场需求。而前面的关于欧洲国家的贸易壁垒，只是作为一个美国需要打开本土市场的background。因为出口不行了，所以需要拉动内需。
反过来把C选项代入题目中，则是美国S产品主要依靠于出口欧洲国家，但是现在遭遇欧洲国家的贸易壁垒，如果政府能增长美国本土需求的话，S产业还是可以生产那么多的产品，因为美国也可以对其他国家设置贸易壁垒。
这样的逻辑我觉得有以下问题：
1. 也就是说，增加的国内需求=出口的产品数量，这样才能使得企业维持原来的生产量。如果没有E选项，那我完全可以假设美国的市场已经开发了一定规模，即使有一些举措刺激消费，很可能达不到出口的数量。
2. 按照C选项，美国增加了需求后，如果设置贸易壁垒，可以防止别国占据市场份额。但是！贸易壁垒是用于防止那些想要进入美国市场的外国企业，题目只说了，欧洲市场会被大多数欧洲生产商占领，并没有明显的说欧洲生产商还想要进入美国市场啊。有可能占据欧洲市场都需要花一些时间和精力了，再说了，美国的消费需求可以被刺激，欧洲也可以呀，题目也没说欧洲的市场达到最大化了，如此一来，欧洲生产商进军美国市场的可能性又低了。也就是说，美国的贸易壁垒没有起到明显的作用。

所以我觉得从根本上来说，是因为市场的开发小，还有潜力可以发掘，才能给美国带来真正的消费需求来保证企业生产量

visan_y

https://www.manhattanprep.com/gmat/forums/united-states-manufacturers-currently-produce-most-of-the-t2412.html

here's a diagram type thingy:
euro companies emerge
AND
euro companies take over euro market
AND
u.s. market emerges
AND
----
THEREFORE
u.s. companies will replace euro market sales with u.s. market sales

we currently have facts asserting that the u.s. firms will lose their hold on the euro market. however, we have nothing asserting that the u.s. firms will gain a hold on the u.s. market, the second half of the conclusion.

therefore, we need an assertion that says, or implies, that the u.s. firms will gain a hold in the u.s. market (i.e., the euro firms won't take over the u.s. market as well).

(a) irrelevant:
- recent increases are unrelated to maintaining production in the future
- recent increases in production have nothing to do with the main logic gap (ensuring that u.s. firms will have a hold on the u.s. market)

(b) irrelevant:
- this has nothing to do with anything related to the argument

(c) correct
this statement strongly suggests that the u.s. firms will dominate the u.s. market for the same reasons that the euro firms will dominate the euro market.

(d) doesn't help
- we know that the u.s. firms will lose the euro market anyway, so it doesn't matter whether that market grows or not

(e) WEAKENS the argument
- if the u.s. market is very small, then it's likely that the production/revenue/etc of u.s. firms will decline rather than stay constant.

--

as far as you query 'what is the best way to arrive at the correct answer': there's clearly not an extremely simple way, since gmac would not bother writing these questions if there were. the best way to figure out the underlying logic is to make a diagram (like the one i made above, with the ands and therefores), which will force you to map out the logic.

拉美

这个题，我一开始也是错选了e，但其实仔细品，the current market for solar-power generators in the United States is very limited，什么叫market 被limit了，其实就是demand  limit---有需求就会有市场啊，需求方，那么题目说了美国居民的需求已经被打开了，这就是否定事实前提---其实是想问你市场被打开了之后，美国生产商能不能把握住机会，果断c