timzhou, 请把文章贴出来，便于大家回复。谢谢！
Hi, you'd better paste the article and the question. Because it will be easy for other persons to answer your questions. For example, now I am on a business trip and it is difficult for me to check the context of your article concerned.
this is my virgin question, thanks all!
According to a recent theory, Archean-age gold-quartz
vein systems were formed over two billion years ago from
magmatic fluids that originated from molten granitelike
bodies deep beneath the surface of the Earth. This theory is
(5) contrary to the widely held view that the systems were
deposited from metamorphic fluids, that is, from fluids that
formed during the dehydration of wet sedimentary rocks.
he recently developed theory has considerable practical
importance. Most of the gold deposits discovered during
(10) the original gold rushes were exposed at the Earth's surface
and were found because they had shed trails of alluvial
gold that were easily traced by simple prospecting methods.
Although these same methods still lead to an occasional
discovery, most deposits not yet discovered have gone
(15) undetected because they are buried and have no surface
expression.
The challenge in exploration is therefore to unravel the
subsurface geology of an area and pinpoint the position of
buried minerals. Methods widely used today include
(20) analysis of aerial images that yield a broad geological
overview; geophysical techniques that provide data on the
magnetic, electrical, and mineralogical properties of the
rocks being investigated; and sensitive chemical tests that
are able to detect the subtle chemical halos that often
(25) envelop mineralization. However, none of these high-
technology methods are of any value if the sites to which
they are applied have never mineralized, and to maximize
the chances of discovery the explorer must therefore pay
particular attention to selecting the ground formations most
(30) likely to be mineralized. Such ground selection relies to
varying degrees on conceptual models, which take into
account theoretical studies of relevant factors.
These models are constructed primarily from empirical
observations of known mineral deposits and from theories
35) of ore-forming processes. The explorer uses the models to
identify those geological features that are critical to the
formation of the mineralization being modeled, and then
tries to select areas for exploration that exhibit as many of
the critical features as possible.
8. It can be inferred from the passage that the efficiency of
model-based gold exploration depends on which of the
following?
Ⅰ. The closeness of the match between the geological
features identified by the model as critical and the
actual geological features of a given area
Ⅱ. The degree to which the model chosen relies on
empirical observation of known mineral deposits
rather than on theories of ore-forming processes
Ⅲ. The degree to which the model chosen is based on
an accurate description of the events leading to
mineralization
(A) Ⅰonly
(B) Ⅱ only
(C) Ⅰand Ⅱ only
(D) Ⅰ and Ⅲ only
(E) Ⅰ,Ⅱ and Ⅲ
observations of known mineral deposits and from theories
35) of ore-forming processes. The explorer uses the models to
identify those geological features that are critical to the
formation of the mineralization being modeled,
我認為此處是關鍵的.說明了模型的準確性從兩方面來.
這是og中的文章把.建議看看og的解釋.很抱歉延遲答覆樓主..
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