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.

麻烦解释一下这个题目？

我来试着翻译一下：

虽然古努比亚人居住在一个伤寒感染区，但十分惊奇的是在他们的骨骼中几乎找不到（曾经感染伤寒）常见的依据。一种有在努比亚的土壤中常见的细菌可以产生四环素，而且在骨骼中也发现遗留有四环素的成分，（进一步发现）这种细菌在努比亚人用于制作2种日常食品（啤酒和干面包）的干缩谷物中非常活跃。因此这些食物中的四环素可以用来解释古努比亚人的伤寒低感染率。

问答案中哪一个是前提

A:四环素对伤寒以外的努比亚人会遇到的传染病无效（无关选项）

B:四环素的抗生素药性不会随着努比亚人的食物加工过程失掉。（正确）

C:伤寒不会通过吃了含有这种病毒的面包或啤酒而感染。（无关）

D:在努比亚认的食物种类中只有面包或者啤酒才能含有四环素。（无关）

E:伤寒一般是无药可医的。(无关）

其实我觉得另外一个更重要的前提是四环素确实可以预防伤寒病。可惜选项没有！

请讨论