41.
A:
Histidine negative (His - ) strain of Salmonella typhimurium
B:
Alanine (ala - ) strain of Salmonella typhimurium
C:
Glycine (gly - ) strain of Salmonella typhimurium
D:
Cysteine negative (cys - ) strain of Salmonella typhimurium
The answer is: A