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?

A.      Infectious diseases other than typhus to which the ancient Nubians were exposed are unaffected by tetracycline.

B.      Tetracycline is not rendered ineffective as an antibiotic by exposure to the processes involved in making bread and beer.

C.      Typhus cannot be transmitted by ingesting bread or beer contaminated with the infectious agents of this disease.

D.      Bread and beer were the only items in the diet of the ancient Nubians which could have contained tetracycline.

E.       Typhus is generally fatal.

答案是B，不解。B表达什么意思呢？另外，弱问C错在哪里？谢谢！！！

Premises: The skeletons do show deposits of tetracycline, an antibiotic produced by a bacterium

Hypothesis: tetracycline in their food probably explains the low incidence of typhus among ancient Nubians

The author attempts to draw the casual relationship from the co presence of tetracycline and low incidence rate for the typhus.

“Tetracycline is not rendered ineffective as an antibiotic by exposure to the processes involved in making bread and beer.” The hypothesis is that tetracycline in their food probably explains the low incidence of typhus among ancient Nubians, so tetracycline is must be effective

“Typhus cannot be transmitted by ingesting bread or beer contaminated with the infectious agents of this disease” C is not an assumption because, even if the Typhus can be transmitted by bread and beer, Tetracycline presented in the same bread and beer can kill it soon.

谢谢啊！

现在有点明白了，

这道题问的假设，应该是在Tetracycline和disease之间建立起一个关系，C根本没提到Tetracycline。。。