质疑 2772-99-No3的答案

snow_mountain

Passage 99 (14/15)

Methods for typing blood were developed around the turn of the century, about the same time that fingerprints were first used for identification. Only in the last decade or two, however, have scientists begun to believe that genetic markers in blood and other bodily fluids may someday prove as useful in crime detection as fingerprints.

The standard ABO blood typing has long been used as a form of negative identification. Added sophistication came with the discovery of additional subgroups of genetic markers in blood and with the discovery that genetic markers are present not only in blood but also in other bodily fluids, such as perspiration and saliva.

These discoveries were of little use in crime detection, however, because of the circumstances in which police scientists must work. Rather than a plentiful sample of blood freshly drawn from a patient, the crime laboratory is likely to receive only a tiny fleck of dried blood of unknown age from an unknown “donor” on a shirt or a scrap of rag that has spent hours or days exposed to air, high temperature, and other contaminants.

British scientists found a method for identifying genetic markers more precisely in small samples. In this process, called electrophoresis, a sample is placed on a tray containing a gel through which an electrical current is then passed. A trained analyst reads the resulting patterns in the gel to determine the presence of various chemical markers.

Electrophoresis made it possible to identify several thousand subgroups of blood types rather than the twelve known before. However, the equipment and special training required were expensive. In addition, the process could lead to the destruction of evidence. For example, repeated tests of a blood-flecked shirt—one for each marker—led to increasing deterioration of the evidence and the cost of a week or more of laboratory time.

It remained for another British researcher, Brian Wrexall, to demonstrate that simultaneous analyses, using an inexpensive electrophoresis apparatus, could test for ten different genetic markers within a 24-hour period. This development made the study of blood and other fluid samples an even more valuable tool for crime detection.


3.The author sets off the word “‘donor’” (line 18) with quotation marks in order to
(A) emphasize that most of the blood samples received by crime laboratories come from anonymous sources
(B) underscore the contrast between the work done in a crime laboratory and that done in a blood bank
(C) call attention to the fact that, because of underfunding, crime laboratories are forced to rely on charitable contributions
(D) show that the word is being used in a technical, rather than a general, sense
(E) indicate that the blood samples received by crime laboratories are not given freely

答案是E。 我选A。

Rather than a plentiful sample of blood freshly drawn from a patient, the crime laboratory is likely to receive only a tiny fleck of dried blood of unknown age from an unknown “donor” on a shirt or a scrap of rag that has spent hours or days exposed to air, high temperature, and other contaminants.

如果我没理解错的话，这句话的意思应该是，这种血液样本跟从病人身上采样的新鲜的， 大量的血液样本不同， 它们可能是一点小小的不知明的T恤或小布条上面的来源不明的干血迹。（这个血迹可能是罪犯的，可能是受害者的，谁知道呢？）

E是一点关系也没有呀。

flora_wang

这个好像是有点问题...我选的是b. 不知道有没有高手能解答???不妨请楼主把标题改清楚点,让安哥哥帮帮忙吧......

二狼神

支持A.

E是明显的无关.