考试网 >> 外语考试 >> GRE >> GRE试题 >> GRE试题:GRE北美试题15

发布时间：2006-06-22 13:28     点击：

    (E) Proteins containing both amino acids and 18O

    25. The passage suggests that the 18O/ 16O/ ratio could be used more successfully as a means of measurement if scientists were able to

    (A) determine the 18O/ 16 O/ ratio in living animals as well as in fossil remains

    (B) locate a greater number of calcareous fossils from the Pleistocene glacial and interglacial cycles

    (C) locate the factors other than temperature fluctuations and isotopic changes in seawater that affect the 18O/16O/ ratio

    (D) arrive at more exact determinations of which amino acids are found in the proteins of living organisms

    (E) isolate the relative effects of temperature fluctuations and isotopic changes in seawater on 18O/16O/ ratios

    26. The information in the passage can be used to answer which of the following questions?

    Ⅰ Do temperature variations and isotopic changes in seawater cause the 18O/16O ratio to shift in the same direction?

    Ⅱ What are the methods used to determine the18 O/16O ratio?

    Ⅲ Is the study of raceminzation reactions useful in estimating climatic changes that occurred during Pleistocene glacial cycles if only one of the two important variables is known?

    (A) Ⅰonly

    (B) Ⅰand Ⅱ only

    (C) Ⅰand Ⅲ only

    (D) Ⅱand Ⅲ only

    (E) Ⅰ,Ⅱ,and Ⅲ

    27. According to the passage, before the recent experiments described in the passage were completed, scientists could

    (A) determine temperatures only for Pleistocene seas

发表评论： 匿名发表 用户名: 查看评论

您将承担一切因您的行为、言论而直接或间接导致的民事或刑事法律责任 留言板管理人员有权保留或删除其管辖留言中的任意内容 本站提醒：不要进行人身攻击。谢谢配合。