36套里EX21的一篇阅读

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One of the questions of interest in the study of the evolution of spiders is whether the weaving of orb webs evolved only once or several times. About half the 35,000 known kinds of spiders make webs; a third of the web weavers make orb webs. Since most orb weavers belong either to the Araneidae or the Uloboridae families, the origin of the orb web can be determined only by ascertaining whether the families are related.

Recent taxonomic analysis of individuals from both families indicates that the families evolved from different ancestors, thereby contradicting Wiehle’stheory. This theory postulates that the families must be related, based on the assumption that complex behavior, such as web building, could evolve only once.According to Kullman, web structure is the only characteristic that suggests a relationship between families. The families differ in appearance, structure of body hair, and arrangement of eyes. Only Uloborids lack venom glands. Further identification and study of characteristic features will undoubtedly answer the question of the evolution of the orb web.


8.
The primary purpose of the passage is to

(A) settle the question of whether orb webs evolved once or more than once

(B) describe scientific speculation concerning anissue related to the evolution of orb webs

(C) analyze the differences between the characteristicfeatures of spiders in the Araneidae and Uloboridae families

(D) question the methods used by earlier investigatorsof the habits of spiders

(E) demonstrate that Araneidae spiders are not relatedto Uloboridae spiders


C、D、E就直接排除了
可是为什么不选A呢？？？觉得全文都在讲是否evolve一次或多次这个问题呀 然后最后回答是多次呀
求助求助

皮皮皮卡丘大人UID：3737259

说说我的想法哈~
A是一个看似很正确的观点，但是A和B作比较的话，显示是B好~那A哪里不足呢？
文章只是把A作为一个问题在一开始抛了出来，并引发出了是否related的问题，然后下面都是在讨论related（虽然是为了回答A），可以看出整个过程在speculate（列举了两个theory），而且最后说这个问题需要futher identification，也说明没有settle掉这个问题~

canie.duUID：3453356

皮皮皮卡丘大人 发表于 2016-8-26 21:14
说说我的想法哈~
A是一个看似很正确的观点，但是A和B作比较的话，显示是B好~那A哪里不足呢？
文章只是把A ...

明白了！谢谢！我之前一直以为问题已经被settle掉了 现在仔细一看还是要futher identification的！