题目内容

The passage supports which of the following statements about the early mill owners mentioned in the second paragraph？

A. They hoped that by creating relatively unattractive “female” jobs they would discourage women from losing interest in marriage and family life.
B. They sought to increase the size of the available labor force as a means to keep men’s to keep men’s wages low.
C. They argued that women were inherently suited to do well in particular kinds of factory work.
D. They thought that factory work bettered the condition of women by emancipating them from dependence on income earned by men.
E. They felt guilty about disturbing the traditional division of labor in family.

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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 unicellu-
lar organisms, are eukaryotic—their large, complex cells
(5) have a well-formed nucles and many organelles. On the
other hand, the true bacteria are prokaryotic cell, 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 ulti-
(10) mately 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
(15) the two forms are different and characteristic of the respec-
tive forms. For example, the amino acid sequences of vari-
ous 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
(20) that the tree of life had only two stems. Moreover, argu-
ments pointing out the extent of both structural and func-
tional differences between eukaryotes and true bacteria
convinced many biologists that the precursors of the
eukaryotes must have diverged from the common
(25)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
(30)from the true bacteria, and it now appears that there are
three stems in the tree of life. New techniques for deter-
mining 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
(35) from a common ancestor, and the reconstruction of ances-
tral versions of genes. These techniques have strongly
suggested that although the true bacteria indeed form. a
large coherent group, certain other bacteria, the archaebac-
teria, which are also prokaryotes and which resemble true
(40) bacteria, represent a distinct evolutionary branch that
far antedates the common ancestor of all true bacteria.
The passage is primarily concerned with______

A. detailing the evidence that has led most biologists to replace the trichotomous picture of living organisms with a dichotomous one
B. outlining the factors that have contributed to the current hypothesis concerning the number of basic categories of living organisms
C. evaluating experiments that have resulted in proof that the prokaryotes are more ancient than had been expected.
D. summarizing the differences in structure and function found among true bacteria, archaebacteria, and eukaryotes
E. formulating a hypothesis about the mechanisms of evolution that resulted in the ancestors of the prokaryotes

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According to the passage, investigations of eukaryotic and prokaryotic cells at the molecular level supported the conclusion that______

A. most eukaryotic organisms are unicellular
B. complex cells have well-formed nuclei
C. prokaryotes and cukaryotes form. two fundamental categories
D. subcellular structures are visible with a microscope
E. prokaryotic and eukaryotic cells have similar enzymes

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阴茎套的避孕原理为

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防止中毒的防护措施有以下几方面

A. 降低车间粉尘浓度
B. 防止皮肤污染
C. 及时清除皮肤污染
D. 就业前体检
E. 可根据经9:1酒精氢氧化钠溶液擦后是否变红，判断有无皮肤污染

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