[求助]GWD-27-4

Two opposing scenarios,

the “arboreal” hypothesis and

the “cursorial” hypothesis, have

Line traditionally been put forward con-

(5)  cerning the origins of bird flight.

The “arboreal” hypothesis holds

that bird ancestors began to fly

by climbing frees and gliding

down from branches with the

(10) help of incipient feathers: the

height of trees provides a good

starting place for launching flight,

especially through gliding. As

feathers became larger over time,

(15) flapping flight evolved and birds

finally became fully air-borne.

This hypothesis makes intuitive

Sense, but certain aspects are

Troubling. Archaeopteryx (the

(20) earliest known bird) and its

maniraptoran dinosaur cousins

have no obviously arboreal

adaptations, such as feet fully

adapted for perching. Perhaps

(25) some of them could climb trees,

but no convincing analysis has

demonstrated how Archaeopteryx

would have both climbed and

flown with its forelimbs, and there

(30) were no plants taller than a few

meters in the environments where

Archaeopteryx fossils have been

found. Even if the animals could

climb trees, this ability is not

(35) synonymous with gliding ability.

(Many small animals, and even

some goats and kangaroos,

are capable of climbing trees

but are not gliders.) Besides,

(40) Archaeopteryx shows no obvi-

ous features of gliders, such as

a broad membrane connecting

forelimbs and hind limbs.

   The “cursorial”(running)

(45) hypothesis holds that small

dinosaurs ran along the ground

and stretched out their arms for

balance as they leaped into the

air after insect prey or, perhaps,

(50) to avoid predators. Even rudi-

mentary feathers on forelimbs

could have expanded the arm’s

surface area to enhance lift

slightly. Larger feathers could

(55) have increased lift incrementally,

until sustained flight was gradu-

ally achieved. Of course, a leap

into the air does not provide the

acceleration produced by drop-

(60) ping out of a tree; an animal

would have to run quite fast

to take off. Still, some small

terrestrial animals can achieve

high speeds. The cursorial

(65) hypothesis is strengthened by

the fact that the immediate the-

ropod dinosaur ancestors of

birds were terrestrial, and they

had the traits needed for high

(70) lift off speeds: they were small,

agile, lightly built, long-legged,

and good runners. And because

they were bipedal, their arms

were free to evolve flapping flight,

(75) which cannot be said for other

reptiles of their time.

A.     Feathers tend to become larger over time

B.     Flapping flight is thought to have evolved gradually over time

C.     Many small animals are capable of climbing trees.

D.     Plants in Archaeopteryx’s known habitats were relatively small

E.      Leaping into the air does not provide as much acceleration as gliding out of a tree

Answer: C D   
我选的是C,根据原文36到39行的括号内的内容.不知道D的对应点在哪里.

 .

Many small animals, and even

some goats and kangaroos,

are capable of climbing trees

but are not gliders，D对应

but no convincing analysis has

demonstrated how Archaeopteryx

would have both climbed and

flown with its forelimbs, and there

(30) were no plants taller than a few

meters in the environments where

Archaeopteryx fossils have been

found.

but no convincing analysis has

demonstrated how Archaeopteryx

would have both climbed and

flown with its forelimbs, and there

(30) were no plants taller than a few

meters in the environments where

Archaeopteryx fossils have been

found.

Two opposing scenarios,

the “arboreal” hypothesis and

the “cursorial” hypothesis, have

Line traditionally been put forward con-

(5)  cerning the origins of bird flight.

The “arboreal” hypothesis holds

that bird ancestors began to fly

by climbing frees and gliding

down from branches with the

(10) help of incipient feathers: the

height of trees provides a good

starting place for launching flight,

especially through gliding. As

feathers became larger over time,

(15) flapping flight evolved and birds

finally became fully air-borne.

This hypothesis makes intuitive

Sense, but certain aspects are

Troubling. Archaeopteryx (the

(20) earliest known bird) and its

maniraptoran dinosaur cousins

have no obviously arboreal

adaptations, such as feet fully

adapted for perching. Perhaps

(25) some of them could climb trees,

but no convincing analysis has

demonstrated how Archaeopteryx

would have both climbed and

flown with its forelimbs,
                and there

(30) were no plants taller than a few

meters in the environments where

Archaeopteryx fossils have been

found. Even if the animals could

climb trees, this ability is not

(35) synonymous with gliding ability.

(Many small animals, and even

some goats and kangaroos,

are capable of climbing trees

but are not gliders.) Besides,

(40) Archaeopteryx shows no obvi-

ous features of gliders, such as

a broad membrane connecting

forelimbs and hind limbs.

答案说D我没意见，但是C也说不上哪里硬是不对。。。黄色部分

题目问得是undermine树栖理论，也就是paraphrase他的不足或严格的要求（1。树(高一点的)2。鸟祖先要能爬上去。3。要能滑翔(膜结构)），在原文共说了以下几点理论的不足：

1。A鸟没有feet adapted for perching木栖。(没发育好)

2。即使有些（发育好的）可以爬树[让步1]，没证据说明可以同时用前肢爬树和飞行。(还是说发育不完美)

3。(好就算你有些牛，发育完美了)[让步2]，那里附近的化石证明没有高的树可以起飞。[这下死心了。。。]

4。[让步3，就算有树吧，也就算你可以爬吧]，谁说爬树和飞之间有必然关联？一些小动物就会爬树，但不会滑翔

GMAT主要考推理中的环环相扣，推理到这里发现其实前两点讨论没有意义。会爬了有怎么样，也不能飞啊：）which means 会or不会爬树，并不能算是undermine 这一理论的不足。C的内容本身没错，但起不了weaken的作用(未正面答题)。

5。此外，A呢也没有明显标志比如膜结构什么的。（所以不能用树栖理论飞）

总结：其实共两点不足可以用来undermine,1.没有高树；2.没有膜结构等滑翔器官 （爬树没考虑进去）

愚见，大家怎么想呢?

要细说的话，Ｃ选项说对于ＭＡＭＭＡＬ说的很笼统，文章说的是那些会爬树，但是不会ＧＬＩＤＩＮＧ的，若Ｃ后面再加一句话就没问题了！

考试时就应该选最优的答案．节省时间．也是ＧＭＡＴ的原则．