题目: The ancient Nubians inhabited an area in which typhus occurred, 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? 答案是A. The tetracycline deposits did not form after the bodies were buried.排除他因 但是我觉得B也可以啊, B: The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline. 请解答 | 
