求教：LSAT-14-2-24

freelance

24. A certain airport security scanner designed to detect explosives in luggage will alert the scanner's operator whenever the piece of luggage passing under the scanner contains an explosive. The scanner will erroneously alert the operator for only one percent of the pieces of luggage that contain no explosives. Thus in ninety-nine out of a hundred alerts explosives will actually by present.

The reasoning in the argument is flawed because the argument

(A) ignores the possibility of the scanner's failing to signal an alert when the luggage does contain an explosive

(B) draws a general conclusion about reliability on the basis of a sample that is likely to be biased

(C) ignores the possibility of human error on the part of the scanner's operator once the scanner has alerted him or her

(D) fails to acknowledge the possibility that the scanner will not be equally sensitive to all kinds of explosives

(E) substitutes one group for a different group in the statement of a percentage

结论这句“Thus in ninety-nine out of a hundred alerts explosives will actually by present.

”没明白

lawyer_1

100个报警中99个的行李中实际有EXPLOSIVES。原文实际是将没EXPLOSIVE的行李的报警错误率1%当作所有行李的报警错误率。从而得出该结论。