Answer:
B. acidity of the vagina
Step-by-step explanation:
The genus Lactobacillus includes rods and coccobacilli that lack catalase and produce lactic acid as the main fermentation product. Lactobacilli grow optimally under slightly acidic conditions. They are part of the normal flora of the human body and are present in the intestinal tract, vagina, etc.
In the human female vagina, the Lactobacilli are rarely pathogenic and rather serve as antimicrobial agents and prevent the growth of pathogenic microbes by imparting acidic pH to the vagina. Production of lactic acid by these bacteria imparts acidic pH and allows them to serve as antimicrobial agents.