请教几道逻辑题的解题思路

(1)In 1986, the city of ffice:smarttags" />Los Diablos had 20 days on which air pollution reached unhealthful amounts and a smog alert was put into effect. In early 1987, new air pollution control measures were enacted, but the city had smog alerts on 31 days that year and on 39 days the following year. In 1989, however, the number of smog alerts in Los Diablos dropped to sixteen. The main air pollutants in Los Diablos are ozone and carbon monoxide, and since 1986 the levels of both have been monitored by gas spectrography.fficeffice" />

Which of the following statements, assuming that each is true, would be LEAST helpful in explaining the air pollution levels in Los Diablos between 1986 and 1989?

(A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988.

(B) In December of 1988 a new and far more accurate gas spectrometer was invented.

(C) In February of 1989, the Pollution Control Board of Los Diablos revised the scale used to determine the amount of air pollution considered unhealthful.

(D) In 1988 the mayor of Los Diablos was found to have accepted large campaign donations from local industries and to have exempted those same industries from air pollution control measures.

(E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.

answer: b

Archaeologists seeking the location of a legendary siege and destruction of a city are excavating in several possible places, including a middle and a lower layer of a large mound. The bottom of the middle layer contains some pieces of pottery of type 3, known to be from a later period than the time of the destruction of the city, but the lower layer does not.

     The force of the evidence cited above is most seriously weakened if which of the following is true?

(A) Gerbils, small animals long native to the area, dig large burrows into which objects can fall when the burrows collapse.

(B) Pottery of types 1 and 2, found in the lower level, was used in the cities from which, according to the legend, the besieging forces came.

(C) Several pieces of stone from a lower-layer wall have been found incorporated into the remains of a building in the middle layer.

(D) Both the middle and the lower layer show evidence of large-scale destruction of habitations by fire.

(E) Bronze ax heads of a type used at the time of the siege were found in the lower level of excavation.

answer: a

(3)For a local government to outlaw all strikes by its workers is a costly mistake, because all its labor disputes must then be settled by binding arbitration, without any negotiated public-sector labor settlements guiding the arbitrators. Strikes should be outlawed only for categories of public-sector workers for whose services no acceptable substitute exists.

The statements above best support which of the following conclusions?

(A) Where public-service workers are permitted to strike, contract negotiations with those workers are typically settled without a strike.

(B) Where strikes by all categories of pubic-sector workers are outlawed, no acceptable substitutes for the services provided by any of those workers are available.

(C) Binding arbitration tends to be more advantageous for public-service workers where it is the only available means of settling labor disputes with such workers.

(D) Most categories of public-sector workers have no counterparts in the private sector.

(E) A strike by workers in a local government is unlikely to be settled without help from an arbitrator.

answer: c

(4)The value of a product is determined by the ratio of its quality to its price. The higher the value of a product, the better will be its competitive position. Therefore, either increasing the quality or lowering the price of a given product will increase the likelihood that consumer will select that product rather than a competing one.

Which of the following, if true, would most strengthen the conclusion drawn above?

(A) It is possible to increase both the quality and the price of a product without changing its competitive position.

(B) For certain segments of the population of consumers, higher-priced brands of some product lines are preferred to the lower-priced brands.

(C) Competing products often try to appeal to different segments of the population of consumers.

(D) The competitive position of a product can be affected by such factors as advertising and brand loyalty

(E) Consumers’ perceptions of the quality of a product are based on the actual quality of the product

answer: e

(5)In the United States, vacationers account for more than half of all visitors to what are technically called “pure aquariums” but for fewer than one quarter of all visitors to zoos, which usually include a “zoo aquarium” of relatively modest scope.

Which of the following, if true, most helps to account for the difference described above between visitors to zoos and visitors to pure aquariums?

(A) In cities that have both a zoo and a pure aquarium, local residents are twice as likely to visit the aquarium as they are to visit the zoo.

(B) Virtually all large metropolitan areas have zoos, whereas only a few large metropolitan areas have pure aquariums.

(C) Over the last ten years, newly constructed pure aquariums have outnumbered newly established zoos by a factor of two to one.

(D) People who visit a zoo in a given year are two times more likely to visit a pure aquarium that year than are people who do not visit a zoo.

(E) The zoo aquariums of zoos that are in the same city as a pure aquarium tend to be smaller than the aquariums of zoos that have no pure aquarium nearby.

answer: b