I think the correct answer from the choices listed above is option B. You can find methanogens in the human intestines. These organisms can work with or without oxygen. Too much of oxygen for them is toxic. They are obligate anaerobes.
Answer:
plasmid
Explanation:
plasmid
The human insulin gene is inserted into each plasmid. The plasmid acts as a vector - it is used to transfer DNA from one organism to another. Bacterial cells are made to take up the genetically modified plasmids.