大全338~~~同位语混乱

If a single strain of plant is used for a given crop over a wide area, a practice fostered by modern seed-marketing methods, it increases the likelihood that the impact of a single crop disease or pest will be disastrous.

(A) If a single strain of plant is used for a given crop over a wide area, a practice fostered by modern seed-marketing methods, it

(B) If a single strain of plant is used for a given crop over a wide area, as is fostered by modern seed-marketing methods, it

(C) A practice fostered by modern seed-marketing methods, a single strain of plant used for a given crop over a wide area

(D) A single strain of plant used for a given crop over a wide area, a practice fostered by modern seed-marketing methods,（E）

(E) The use of single strain of plant for a given crop over a wide area, a practice fostered by modern seed-marketing methods,

Choice A is faulty because the pronoun it and the appositive a practice each lack a noun referent. Nor are there logical referents in choice B for as is and it. Choice C entails a false appositive: the sentence now says that the single strain of plant is itself a practice fostered by modern seed-marketing methods, not that the use of a single strain is such a practice. Choice D reverses the order of the constructions, but the appositive remains illogical. Choice E is correct: use is the proper subject for the verb increases and a logical governing noun for the appositive practice. This question is of middle difficulty.

看了以前的讨论，说同位语可以用来修饰前面的整个句子，那么D为什么不对呢

还是同位语必须有一个相应的中心名词？

请NN指教

再加一题GWD1-16,结合看看

Soaring television costs accounted for more than half the spending in the presidential campaign of 1992, a greater proportion than it was in any previous election.

1. a greater proportion than it was
   
2. a greater proportion than
   
3. a greater proportion than they have been
   
4. which is greater than was so
   
5. which is greater than it has been

这题好像争来争去都没确定结果

从同位语角度来看，a greater propotion than it was in any previous election，修饰整个句子，构成独立的部分

it 指代propotion，选项A比较合理，一下子又搞不清什么时候用that指代什么时候用it

NN不吝指教~~~~鞠躬

Choice C entails a false appositive: the sentence now says that the single strain of plant is itself a practice fostered by modern seed-marketing methods, not that the use of a single strain is such a practice.

D不对的原因和C一样    practice的同位语只能是应用（use） 不能是变种本身

顺便附上对strain的解释：Strain (biology), a variant of a plant, virus or bacterium; or an inbred animal used for experimental purposes

(D) A single strain of plant used for a given crop over a wide area, a practice fostered by modern seed-marketing methods,

a single strain cannot be equaled with a practice, and this is why D is not the right choice