求助新prep-74，86，98

In
a certain wildlife park, park rangers are able to track the movements of many
rhinoceroses because those animals wear radio collars.  When, as often happens, a collar slips off,
it is put back on.  Putting a collar on a
rhinoceros involves immobilizing the animal by shooting it with a tranquilizer
dart.  Female rhinoceroses that have been
frequently recollared have significantly lower fertility rates than uncollared
females.  Probably, therefore, some
substance in the tranquilizer inhibits fertility.

In
evaluating the argument, it would be most useful to determine which of the
following?

A.
Whether there are more collared female rhinoceroses than uncollared female
rhinoceroses in the park

B.
How the tranquilizer that is used for immobilizing rhinoceroses differs, if at
all, from tranquilizers used in working with other large mammals

C.
How often park rangers need to use tranquilizer darts to immobilize
rhinoceroses for reasons other than attaching radio collars

D.
Whether male rhinoceroses in the wildlife park lose their collars any more
often than the park’s female rhinoceroses do

E.
Whether radio collars are the only practical means that park rangers have for
tracking the movements of rhinoceroses in the park

答案是c，可是如果只是知道用于其他目的镇静剂使用频率，并不能加强或削弱原文推理啊（即镇静剂中某种成分使生殖力降低），我觉得五个都不对，正确答案应该是看是否有别的因素在影响。

86.   (24835-!-item-!-188;#058&001244)

Which
of the following most logically completes the passage?

Concerned
about the financial well-being of its elderly citizens, the government of
Runagia decided two years ago to increase by 20 percent the government-provided
pension paid to all Runagians over 65. 
Inflation in the intervening period has been negligible, and the
increase has been duly received by all eligible Runagians.  Nevertheless, many of them are no better off
financially than they were before the increase, in large part because
__________.

A.
they rely entirely on the government pension for their income

B.
Runagian banks are so inefficient that it can take up to three weeks to cash a
pension check

C.
they buy goods whose prices tend to rise especially fast in times of inflation

D.
the pension was increased when the number of elderly Runagians below the
poverty level reached an all-time high

E.
in Runagia children typically supplement the income of elderly parents, but
only by enough to provide them with a comfortable living

答案是e，可是e成立有一个条件就是上涨之后生活仍不足以达到舒适的水平， 相较之下c更有说服力

98.   (32682-!-item-!-188;#058&006783)   

Early
in the twentieth century, Lake
                Konfa became very
polluted.  Recently fish populations have
recovered as release of industrial pollutants has declined and the lake’s
waters have become cleaner.  Fears are
now being voiced that the planned construction of an oil pipeline across the
lake’s bottom might revive pollution and cause the fish population to decline
again.  However, a technology for
preventing leaks is being installed. 
Therefore, provided this technology is effective, those fears are
groundless.

The
argument depends on assuming which of the following?

A.
Apart from development related to the pipeline, there will be no new industrial
development around the lake that will create renewed pollution in its waters.

B.
There is no reason to believe that the leak-preventing technology would be
ineffective when installed in the pipeline in Lake
                Konfa.

C.
The bottom of the lake does not contain toxic remnants of earlier pollution
that will be stirred into the water by pipeline construction.

D.
Damage to the lake’s fish populations would be the only harm that a leak of oil
from the pipeline would cause.

E.
The species of fish that are present in Lake
                Konfa
now are the same as those that were in the lake before it was affected by
pollution.

答案是c没有意见，a错在哪里啊？