Asequencing of the dna of bacterial samples obtained from normal human stomachs compared with the dna of bacterial samples obtained from individuals infected with the bacterium h. pylori determined that

The correct answer is "most of the sequences from infected individuals belonged to the phylum proteobacteria".
It has been shown that there are significant differences between the microbiome of H. pylori-negative individuals (people who were not infected by the bacterium H. pylori) and H. pylori-positive individuals (people whose stomachs were infected with this bacterium).

More specifically, the H. pylori individuals had a highly diverse gastric microbiota, which was comprised of five different phyla of microorganisms: Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, and Fusobacteria.

On the other hand, the H. pylori individuals had a much less diverse gastric microbiota. This is because the bacterium H. pylori accounted for 72-97% of the microbes in the stomach of the infected individuals. Given that H. pylori belongs to the phylum of Proteobacteria, most of the sequences of the infected individuals belonged to the phylum of Proteobacteria.

answer: - b cells

explanation: -

there are many types of white blood cells present in our body. one such class of white blood cells are the lymphocytes. the b cells belong to the lymphocyte class of wbcs. the b cells perform their action against the pathogen by producing specialised proteins called as antibodies. these antibodies are produced as and when the b cells encounter pathogens in response to the antigens present on the surface of the pathogen. these antibodies bind to the antigens present on the pathogen and then, target them for destruction by other cells of the immune system.

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.