Approximately 99% of the microbes in the intestines are obligate anaerobes. we have plenty of blood vessels that can bring oxygen to the tissues of the intestines. why would there be obligate anaerobes within these areas? a. the bacteria in the intestines are protected from exposure to the oxygen in the tissues by the lining of the intestines. b. the bacteria consume all the oxygen in the tissue areas brought by the blood vessels, creating an anaerobic environment. c. while the blood vessels supply oxygen to the tissues of the intestines, the inner area where the bacteria reside is not supplied with blood/oxygen. since it's deep within our bodies, there's no chance for oxygen to get into these inner areas of the intestinal tube, creating a highly anaerobic environment. d. the aerobic microbes are outcompeted for nutrients in these areas by the anaerobic microbes.

The correct answer is option C.

Explanation:

The human gastrointestinal microbiota or the gut microbiota or the gut flora refers to the microbes, which thrive in the digestive tracts of humans. The human gastrointestinal tract comprises the gathering of all the genomes of gut microbiota. It is the niche where the human microbiota is found.  

The microbial composition of the gut microbiota differs across the digestive tract. In the small intestine and stomach, very small species of bacteria are found, while the colon comprises the densely populated microbial ecosystem. Of these over 99 percent of the bacteria found in the gut are anaerobes, as the space within the intestines is highly anaerobic.  

These microbes are confined deep within the body where oxygen cannot reach as it is not supplied with the help of blood vessels. Thus, a highly anaerobic environment is witnessed deep within the intestinal regions.  

it has one origin of replication, but it proceeds in two directions - d)