考到了GWD这道题：
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.
选项有几个跟原题有点不一样。