新G阅读36套 exercise12中的一道阅读题

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    The determination of the sources of copper ore used in the manufacture of copper and bronze artifacts of Bronze Age civilizations would add greatly to our knowledge of
Line cultural contacts and trade in that era. Researchers have
5 analyzed artifacts and ores for their concentrations of elements, but for a variety of reasons, these studies have generally failed to provide evidence of the sources of the copper used in the objects. Elemental composition can vary within the same copper-ore lode, usually because of varying admixtures of
10 other elements, especially iron, lead, zinc, and arsenic. And high concentrations of cobalt or zinc, noticed in some artifacts, appear in a variety of copper-ore sources. Moreover, the processing of ores introduced poorly controlled changes in the concentrations of minor and trace elements in the
15 resulting metal. Some elements evaporate during smelting and roasting; different temperatures and processes produce different degrees of loss. Finally, flux, which is sometimes added during smelting to remove waste material from the ore, could add quantities of elements to the final product.
      20 An elemental property that is unchanged through these chemical processes is the isotopic composition of each metallic element in the ore. Isotopic composition, the percentages of the different isotopes of an element in a given sample of the element, is therefore particularly suitable as an
25 indicator of the sources of the ore. Of course, for this purpose it is necessary to find an element whose isotopic composition is more or less constant throughout a given ore body, but varies from one copper ore body to another or, at least, from one geographic region to another.
     30 The ideal choice, when isotopic composition is used to investigate the source of copper ore, would seem to be copper itself. It has been shown that small but measurable variations occur naturally in the isotopic composition of copper. However, the variations are large enough only in rare
35 ores; between samples of the common ore minerals of copper, isotopic variations greater than the measurement error have not been found. An alternative choice is lead, which occurs in most copper and bronze artifacts of the Bronze Age in amounts consistent with the lead being derived from the
40 copper ores and possibly from the fluxes. The isotopic composition of lead often varies from one source of common copper ore to another, with variations exceeding the measurement error; and preliminary studies indicate virtually uniform isotopic composition of the lead from a
45 single copper-ore source. While some of the lead found in an artifact may have been introduced from flux or when other metals were added to the copper ore, lead so added in Bronze Age processing would usually have the same isotopic composition as the lead in the copper ore. Lead isotope
50 studies may thus prove useful for interpreting the archaeological record of the Bronze Age.
(473 words)



7. It can be inferred from the passage that the use
of flux in processing copper ore can alter the
lead isotope composition of the resulting metal
EXCEPT when （烦人的except题）
(A) there is a smaller concentration of lead in
the flux than in the copper ore
(B) the concentration of lead in the flux is
equivalent to that of the lead in the ore
(C) some of the lead in the flux evaporates
during processing
(D) any lead in the flux has the same isotopic
composition as the lead in the ore （陈虎平老师给的答案是D，原因line45，while some of the lead found ...）（另外一个解释是，any是绝对词）
(E) other metals are added during processing

理解不了，大家能帮忙解释一下吗？求助做过的人，说一下你们的理解啊！谢谢