请教大全44第6题，感谢

yejinleaf

Passage 44 (44/63)

It was once assumed that all living things could be divided into two fundamental and exhaustive categories. Multicellular plants and animals, as well as many unicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleus and many organelles. On the other hand, the true bacteria are prokaryotic cell (prokaryotic cell: 原核细胞), which are simple and lack a nucleus. The distinction between eukaryotes and bacteria, initially defined in terms of subcellular structures visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding. But even where the molecular processes are the same, the details in the two forms are different and characteristic of the respective forms. For example, the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic. The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems. Moreover, arguments pointing out the extent of both structural and functional differences between eukaryotes and true bacteria convinced many biologists that the precursors of the eukaryotes must have diverged from the common ancestor before the bacteria arose.

Although much of this picture has been sustained by more recent research, it seems fundamentally wrong in one respect. Among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life. New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria (archaebacteria: [复] n.[微]原始细菌( 一种不同于细菌和动植物细胞且要求完全厌氧条件并能产生甲烷的微生物)), which are also prokaryotes and which resemble true bacteria, represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria.

6.     According to the passage, researchers working under the two-category hypothesis were correct in thinking that

(A) prokaryotes form a coherent group

(B) the common ancestor of all living things had complex properties

(C) eukaryotes are fundamentally different from true bacteria

(D) true bacteria are just as complex as eukaryotes（C）

(E) ancestral versions of eukaryotic genes functioned differently from their modern counterparts

答案说C，个人认为是A。

A在原文的定位：the true bacteria indeed form a large coherent group,

C在原文有相反的描述：prokaryotic and eukaryotic cells have many features in common

请各位NN不吝赐教。

starist

个人意见如下：

题目的重点在于2分法为什么对了。

2分法对就对在eu-k和pro-k的区分是正确的。——C题支的指向。原文中C的相反描述是明显的让步，后面有标准的强转折But...支持C

而2分法和3分法的分歧就在于pro-k中可以分成true-b和archae-b。而A的题支正好就是这方面的争议。而原文这句也是让步，前面的Although提示了Certain后面的才是3分法的意见(有可能正确的意见)。

这题让步考的太BT了。

starist

个人对这篇的第5题争议：

5.     If the “new techniques” mentioned in line 31 were applied in studies of biological classifications other than bacteria, which of the following is most likely?

(A) Some of those classifications will have to be reevaluated.

(B) Many species of bacteria will be reclassified.

(C) It will be determined that there are four main categories of living things rather than three.

(D) It will be found that true bacteria are much older than eukaryotes.（A）

(E) It will be found that there is a common ancestor of the eukaryotes, archaebacteria, and true bacteria.

A和B都有相关bacteria大类需要调整导致2分法变3分法的意思。我觉得B明显更具体直接的靠近原文，比标准答案A好。请NN解。