conclusion : tetracycline in food explains the low incidence of typhus among ancient Nubians.

Premise 1: skeletons do show deposits of tetracyclinean antibiotic produced by a bacterium common in Nubian soil.

Premise 2: This bacterium can flourish on the dried grain used for making two staples of the Nubian diet, beer and bread.

A. The tetracycline deposits did not form after the bodies were buried.
--> one of the premise already state that "skeletons show the usual evidence of this disease", so option A cannot be true

B. The diseases other than typhus to which the ancient Nubians were exposed would not be affected by tetracycline.
--> Out of scope nothing talking about another diseases

C. Typhus is generally fatal.
--> Doesnot strengthe the conclusion.

D. Tetracycline is not rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
--> Provide additional evidence that will strength the conclusion. If the Tetracycline which acts as antibiotic is not destroyed in the process of making bread or beer, then we can correctly conclude that
tetracycline in food probably explains the low incidence of typhus.
Correct

using ANT
Tetracycline is rendered ineffective as an antibiotic by exposure to the process involved in making bread and beer.
This clearly contradicts the conclusion, if Tetracycline doesnot act as antibiotic, then incidence of typhus would have been higher

E. Bread and beer were the only foods eaten by the ancient Nubians which could have contained tetracycline.
--> wrong because thay cannot be only source as they were made from grains and bacterium flourished on the dried grain.