The general density dependence model can be applied to explain the founding of specialist firms (those attempting to serve a narrow target market).  According to this model, specialist foundings hinge on the interplay between legitimation and competitive forces, both of which are functions of the density (total number) of firms in a particular specialist population.  Legitimation occurs as a new type of firm moves from being viewed as unfamiliar to being viewed as a natural way to organize.  At low density levels, each founding increases legitimation, reducing barriers to entry and easing subsequent foundings.  Competition occurs because the resources that firms seek--customers, suppliers, and employees--are limited, but as long as density is low relative to plentiful resources, the addition of another firm has a negligible impact on the intensity of competition.  At high density levels, however, competitive effects outweigh legitimation effects, discouraging foundings.  The more numerous the competitors, the fiercer the competition will be and the smaller will be the incentive for new firms to enter the field.

While several studies have found a significant correspondence between the density dependence model and actual patterns of foundings, other studies have found patterns not consistent with the model.  A possible explanation for this inconsistency is that legitimation and competitive forces transcend national boundaries, while studies typically restrict their analysis to the national level.  Thus a national-level analysis can understate the true legitimation and competitive forces as well as the number of foundings in an industry that is internationally integrated.  Many industries are or are becoming international, and since media and information easily cross national borders, so should legitimation and its effects on overseas foundings.  For example, if a type of firm becomes established in the United States, that information transcends borders, reduces uncertainties, and helps foundings of that type of firm in other countries.  Even within national contexts, studies have found more support for the density dependence model when they employ broader geographic units of analysis--for example, finding that the model's operation is seen more clearly at the state and national levels than at city levels.

第一段解释了这个model

第二段说还是有些不符合的research results，那是因为这个study要求的范围足够大--》其实这个模型还是成立的

In the second paragraph, the author is primarily concerned with

(A) noting various exceptions to a certain general finding

(B) examining the impact of one type of industry on another

(C) proposing a possible explanation for an inconsistency

(D) providing specific examples of a particular phenomenon

(E) defending the validity of a particular study's conclusions

The primary purpose of the passage is to

(A) question the validity of an economic model

(B) point out some inconsistencies within an economic model

(C) outline an economic model and suggest revisions to it

(D) describe an economic model and provide specific examples to illustrate its use

(E) explain why an economic model remains valid despite inconsistent research results

第5题问的是第二段作用，如果按答案来说那就是解释为什么不一样

第7题问全文主旨，我想第一段真是纯粹介绍什么别的用都没有吧。。。那第二段怎么单独拎出来的时候就变成了解释inconsistency?

今天仔细看了OG12前面阅读的介绍指导

里面提到单独一段或者一句话或者一个例子的function是和main idea不一样的

所以可能在问part的作用的时候如果看到答案是和main idea很接近了，就要怀疑一下不能贸然选...

我只能得出这个结论了...