Although many lines of evidence indicate

that birds evolved from ground-dwelling

theropod dinosaurs, some scientists remain

Line unconvinced. They argue that theropods(主题：鸟是否由t恐龙进化而来)

(5) appeared too late to have given rise to birds,（反对者：最早的t化石比最早的鸟A化石晚）

noting that Archaeopteryx lithographica—the

oldest known bird—appears in the fossil

record about 150 million years ago, whereas

the fossil remains of various nonavian

(10) maniraptor theropods—the closest known

relatives of birds—date only to about 115

million years ago. But investigators have （但最近发现了和A同时代的t化石）

now uncovered bones that evidently belong

to nonavian maniraptors dating to the time of

(15) Archaeopteryx. In any case, failure to find

fossils of a predicted kind does not rule out

their existence in an undiscovered deposit. （因此，没发现一种化石不能证明其不存在

Skeptics also argue that the fused连着的 clavicles锁骨

(the “wishbone叉骨”) of birds differ from the （怀疑者又说鸟的锁骨连着t的分开）

(20) unfused clavicles of theropods. This

objection was reasonable when only early

theropod clavicles had been discovered,

but fossilized theropod clavicles that look （但那时早期的t

just like the wishbone of Archaeopteryx （现在发现了晚期t的化石锁骨也连着）

(25) have now been unearthed. Finally, some

scientists argue that the complex lungs of（最后，又有人说t的肺进化不成鸟的肺）

birds could not have evolved from theropod

lungs, an assertion that cannot be supported

or falsified at the moment, because no fossil （但是由于肺没有化石，所以无法证明

(30) lungs are preserved in the paleontological

record.

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Q5: The primary purpose of the passage is to

A. compare the development of two hypotheses concerning the evolutionary origin of birds

B. suggest revisions to the standard theory of the evolutionary history of birds

C. evaluate the usefulness of fossil evidence in determining the evolutionary history of birds

D. challenge the theory that birds evolved from ground-dwelling theropod dinosaurs

theropod dinosaurs