[問題] 想請教一題閱讀
題目
The passage suggests which of the following about the "conventional methods"
mentioned in line 2?
(A) They consist primarily of feild surveys and laboratory measurements.
(B) They are not useful in providing information neccessary for reconstructing
geologic evolution.
(C) They have rarely been used by geologists since 1972.
(D) They are used primarily to gather compositional information about geologic
features.
(E) They are limited primarily because of difficulties involved in interpreting
film images.
解答為(A)，疑惑為什麼不能是(D)，謝謝!
原文
Landsat MSS data are now being applied to a variety of geologic problems
that are difficult to solve by conventional methods alone. These include
specific problems in mineral and energy resource exploration and the charting
of glaciers and shallow seas.
A more fundamental application of remote sensing is to augment conventional
methods for giologic mapping of large areas. Regional maps present
compositional, structural, and chronological information for reconstructing
geologic evolution. Such reconstructions have important practical applications
because the conditions under which rock units and other structural features
are formed influence the occurrence of ore and petroleum deposits and affect
the thickness and integrity of the geologic media in which the deposits
are found.
Geologic maps incorporate a large, varied body of specific field and laboratory
measurements, but the maps must be interpretative because field measurements
are always limited by rock explosure, accessibility and labor resources.
With remote-sensing techniques it is possible to obtain much geologic
information more effitiantly than it can be obtained on the ground. These
techniques also facilitate overall interpretation. Since detailed geologic
mapping is generally conducted in small areas, the continuity of regional
features that have intermittent and variable expression is often not recognized,
but in the comprehensive views of Landsat images these continuities are
apparent. However, some critical information cannot be obtained through
remote sensing, and several characteristics of the Landsat MMS impose
limitations on the acquisition of diagnostic data. Some of these limitations
can be overcome by designing satellite systems specifically for geologic
purposes; but, to be most effective, remote-sensing data must still be combined
with data from field surveys and laboratory tests, the techniques of the
earlier twentieth century.
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