下面几道题做了几次还是会错。可以为我作出解释吗？谢谢

GWD-18-Q30

The ancient Nubians inhabited an area in which typhus occurs, yet surprisingly few of their skeletons show the usual evidence of this disease.  The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium common in Nubian soil.  This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread.  Thus, tetracycline in their food probably explains the low incidence of typhus among ancient Nubians.

Which of the following is an assumption on which the argument relies?

1. Infectious diseases other than typhus to which the ancient Nubians were exposed are unaffected by tetracycline.
2. Tetracycline is not rendered ineffective as an antibiotic by exposure to the processes involved in making bread and beer.
3. Typhus cannot be transmitted by ingesting bread or beer contaminated with the infectious agents of this disease.
4. Bread and beer were the only items in the diet of the ancient Nubians which could have contained tetracycline.
5. Typhus is generally fatal.

        GWD-21-Q38

Because it was long thought that few people would watch lengthy televised political messages, most televised political advertisements, like commercial advertisements, took the form of short messages. Last year, however, one candidate produced a half-hour-long advertisement. During the half hour the advertisement was aired, a substantial portion of the viewing public tuned into the advertisement. Clearly, then, many more people are interested in watching lengthy televised political messages than was previously thought.

Which of the following is an assumption on which the argument depends?

      A.     The candidate’s ratings improved significantly as a result of the half-hour-long political advertisement.

      B.     Political advertisements have become increasingly influential in determining voters’ decisions at the polls.

      C.     Many people would appreciate the opportunity to become better acquainted with political candidates’ views on current political issues.

      D.     Most people who are interested in political issues watch television regularly.  

      E.      Most of the viewers who tuned in to the candidate’s half-hour-long advertisement last year did not change channels after the first few minutes.

     GWD-23-Q32

Excavations of the Roman city of Sepphoris have uncovered numerous detailed mosaics depicting several readily identifiable animal species:  a hare, a partridge, and various Mediterranean fish.  Oddly, most of the species represented did not live in the Sepphoris region when these mosaics were created.  Since identical motifs appear in mosaics found in other Roman cities, however, the mosaics of Sepphoris were very likely created by traveling artisans from some other part of the Roman Empire.
Which of the following is an assumption on which the argument depends?

    A.The Sepphoris mosaics are not composed exclusively of types of stones found naturally in the Sepphoris area.

    B. There is no single region to which all the species depicted in the Sepphoris mosaics are native.

    C.No motifs appear in the Sepphoris mosaics that do not also appear in the mosaics of some other Roman city.

    D.All of the animal figures in the Sepphoris mosaics are readily identifiable as representations of known species.

    E.There was not a common repertory of mosaic designs with which artisans who lived in various parts of the Roman Empire were familiar.

        GWD-21-Q38

Because it was long thought that few people would watch lengthy televised political messages, most televised political advertisements, like commercial advertisements, took the form of short messages. Last year, however, one candidate produced a half-hour-long advertisement. During the half hour the advertisement was aired, a substantial portion of the viewing public tuned into the advertisement. Clearly, then, many more people are interested in watching lengthy televised political messages than was previously thought.

Which of the following is an assumption on which the argument depends?

      A.     The candidate’s ratings improved significantly as a result of the half-hour-long political advertisement.

      B.     Political advertisements have become increasingly influential in determining voters’ decisions at the polls.

      C.     Many people would appreciate the opportunity to become better acquainted with political candidates’ views on current political issues.

      D.     Most people who are interested in political issues watch television regularly.  

      E.      Most of the viewers who tuned in to the candidate’s half-hour-long advertisement last year did not change channels after the first few minutes.

     GWD-23-Q32

Excavations of the Roman city of Sepphoris have uncovered numerous detailed mosaics depicting several readily identifiable animal species:  a hare, a partridge, and various Mediterranean fish.  Oddly, most of the species represented did not live in the Sepphoris region when these mosaics were created.  Since identical motifs appear in mosaics found in other Roman cities, however, the mosaics of Sepphoris were very likely created by traveling artisans from some other part of the Roman Empire.
Which of the following is an assumption on which the argument depends?

    A.The Sepphoris mosaics are not composed exclusively of types of stones found naturally in the Sepphoris area.

    B. There is no single region to which all the species depicted in the Sepphoris mosaics are native.

    C.No motifs appear in the Sepphoris mosaics that do not also appear in the mosaics of some other Roman city.

    D.All of the animal figures in the Sepphoris mosaics are readily identifiable as representations of known species.

    E.There was not a common repertory of mosaic designs with which artisans who lived in various parts of the Roman Empire were familiar.