prep争议题，求解答

宋痂岛__

不同意选D 认为选C没有问题

宋痂岛__

but前的comma已经消除了歧义，but后的名词不可能与comma前的名词平行.

顿东w

看一下！               

三颗飞星

我觉得D， 首先are ..., but are.. 和 are not..., but... 平行都是对的。
但是因为not...but...封闭结构如果成立后面应该加个冠词the 和前面保持平行。
即，the products 和 the by-products 平行。
而原文中没有the 就考虑第一种平行。

Daniel100

here is the explanation from RON:


basically, here's the difference:

• "not X but Y":
this construction implies that X is what's "normal" or "expected", and that Y is what's actually true.
e.g.,
I was surprised to learn that Ella was not Clint's biological daughter but in fact his adopted daughter, since her facial features so closely resemble his.
(here, since the girl looks so much like her dad, we EXPECT to find out that she's his biological daughter.)

• "X but Y":
this just implies a contrast, but NOT any expectation.
(in THIS PARTICULAR sentence—as already explained in this thread—the "X" part includes the word "not".)
e.g.,
I am not a mechanic, but can perform basic maintenance on non-hybrid cars.

__

this sentence DOES describe a contrast—these things aren't products of natural selection, BUT they ARE products of essentially random selection processes.

on the other hand, it DOES NOT describe any sort of situation with an "expected" or "predictable" result.

thus it should not use the first construction; it should use the second one.
to make this sentence into "X, but Y", we need to include the are on the right-hand side.

SuperZK

From beat the Gmat
Quote
I received a PM asking me to comment.

In C, the meaning is not crystal clear:

...products of natural selection, favored...but simply random...

The construction above could imply -- incorrectly -- that both favored and random modify products.

In D, the parallel structure are not...but are makes it crystal clear that random refers not to products but to traits:

...traits that are not the products of natural selection...but are simply random by-products of other evolutionary developments...

It must be clear what a modifier is modifying. Since D makes the meaning crystal clear, eliminate C and choose D.
Unquote