一个关于有关无关的问题

一个关于有关无关的问题，望各位赐教，谢谢！

请先看OG11 － 3

3.     “Life expectancy” is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at an age that we now consider the prime of life.

Which of the following, if true, undermines the argument above?

(A) In the middle of the nineteenth century, the population of North America was significantly smaller than it is today.

(B) Most of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life.

(C) Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century.

(D) The proportion of people who die in their seventies is significantly smaller today than is the proportion of people who die in their eighties.

(E) More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today.

Argument Evaluation

Situation         Life expectancy for mid-nineteenth-century North Americans was 40 years; now it is almost 80. What we think of as the prime of life must have been considered old in that earlier era.

Reasoning       What point weakens this argument? The argument relies on the logic of having a great many more 80-year-old people in the population now than was the case 150 years ago. What would challenge this logic? The argument is built upon the average age at death and uses a definition of life expectancy that embraces the entire population of those born alive. What if, in the nineteenth century, the number of infants born alive but not surviving their first year was far higher than it is today? Then the average age at time of death could be significantly reduced by a very large number of infant deaths. On the basis of such information about infant mortality rates, it would not be fair to assume that what today is considered the prime of life was in that earlier time considered old.

A     The size of the population is irrelevant to the argument.

B     Correct. This statement properly identifies the factor that undermines the argument: it was falsely assumed that age for an entire population was simply extended when actually the average age at time of death was significantly raised when the number of infants dying in their first year was reduced.

C     This point supports rather than weakens the argument.

D     This point supports the argument.

E      The regular exercise of one of the two populations compared does not affect the argument.

The correct answer is B.

根据官方解释，C选项的medical technology是导至加强结论，而非WEAKEN。

然后请再看看OG11 － 12

12.   Cable-television spokesperson: Subscriptions to cable television are a bargain in comparison to “free” television. Remember that “free” television is not really free. It is consumers, in the end, who pay for the costly advertising that supports “free” television.

Which of the following, if true, is most damaging to the position of the cable-television spokesperson?

(A) Consumers who do not own television sets are less likely to be influenced in their purchasing decisions by television advertising than are consumers who own television sets.

(B) Subscriptions to cable television include access to some public-television channels, which do not accept advertising.

(C) For locations with poor television reception, cable television provides picture quality superior to that provided by free television.

(D) There is as much advertising on many cable-television channels as there is on “free” television channels.

(E) Cable-television subscribers can choose which channels they wish to receive, and the fees.

Argument Evaluation

Situation         A cable-television spokesperson argues that cable fees are a bargain since so-called “free” television is actually paid for by consumers who underwrite the cost of advertising.

Reasoning       Which point weakens the spokesperson’s argument? The spokesperson’s argument compares the bargain price of a subscription to cable television with the “price” of the costly advertising on “free” television. Consider what situation would undermine this comparison. What if cable television airs just as much advertising as “free” television in addition to the subscription fee? Then the cable subscriber is paying twice, and the spokesperson’s argument that cable television is a bargain in comparison to “free” television is weakened.

A     People who do not watch television are irrelevant to the argument.

B     The fact that cable television subscriptions include access to advertising-free public-television channels does not weaken the argument that “free” television is not free.

C     The picture quality of cable and free television are not at issue in this argument.

D     Correct. This statement properly identifies a factor that weakens the spokesperson’s argument: since the advertising on “free” television acts as a kind of fee, the presence of similar advertising on many cable channels is necessarily the same kind of hidden cost.

E      Consumer choice is not an issue in this argument.

The correct answer is D.

根据官方解释，C选项的picture quality根題目无关。

比较以上两个问题，第3题的medical technology被理解為是加強的元素，然而第12题的picture quality卻是无关选项？到底我們在做题时如何区分有关无关？

以上请指教，先谢谢！