Until now, scientists have depended on measurements of oxygen and carbon isotopes to determine their age, but Pascale Poussart, a geochemist at Princeton University in New Jersey, and her colleagues, have shown that an apparently ring less Miliusa velutina tree(野独活)from Thailand does have rings... they're just invisible.

　　Using X-ray beams focused on wood samples, there searchers looked at calcium, a mineral that trees take up during their main growing season. They revealed annual peaks dating back to 1909.Although the results were in line with carbon isotope measurements,(关于新方法，何者是对的) the calcium method is much quicker.　　"It took us just one afternoon in the synchrotron to produce the record," (方法最大的优点) says Poussart. "The isotope record cost four months of lab time."

　　The team doesn't yet know whether seasonal calcium cycles are common, (如何使新方法普遍接受) or if the feature is specific to just a few types of trees. And it is unclear whether periods of drought, or the modest and patchy dry seasons that feature in some areas of the tropics, will make the signal undecipherable. In search of answers, Poussart will be working with scientists at the Smithsonian Tropical Research Institute's Center for Tropical Forest Science, who runs long-term forest monitoring programmers in Africa, Asia and Latin America.

　　At the moment, much about tropical systems is a mystery, so anything that helps measure time will make an important contribution to the understanding of tropical forest dynamics.

　　题目：

　　1. 主旨题

　　#提出一个新方法，并说明其有缺陷#

　　2.第二段与第一段：新老办法对比

　　参考答案：calcium方法没有炭氧法那么well-established.

　　3.下列哪一个是undermine第一段所说"热带树林 is too subtle to 显示气候的迹象"?　　参考答案：在泰国地区，发现了三种新型态的热带树林，他们的年轮痕迹是用肉眼就可以看出来的

　　4.下列哪种情况学者会比较支持第二段那个人calcium的方法

　　参考答案：如果知道季节在哪种情况下会对年轮辨识度影响较大

　　5.问文章最后一句话(这种collaboration)infer

　　参考答案：选对此方法需进一步验证其有效性

　　6.问从文章可以infer什么?

　　参考答案：方法可以测树的年龄

　　7.这种方法最大的优点

　　省时间

　　8.问关于这个科学家题出的新方法何者正确

　　Tree830224 7/13

　　Q1. If which of the following has been proved, P科学家的Cal方法will be widely accepted?

　　A. It can be determined the drought season willmore affect decipher than dry seasons;

　　B. all the tropical trees have been provedto be different with regard to seasonal calcium cycles;

　　Q2. 主旨题

　　evaluate the reliability of a new method withregard to determining the climate change

　　Q3. which is true about the two methods?

　　A. carbon method is more established than P’smethod;

　　B. P has used x-ray to test carbon(这里注意是carbon, P的新方法是关注calcium)

　　C. Carbon is more accurate in determining theage

　　选项有很多都是carbon出现的，要当心;

　　Q4. Which can be inferred from the passage?

　　选项：P’s method needs further study to check its efficiency;