Answer: Bacteria
Step-by-step explanation:
Some population of bacteria live in the large intestine that are known as good bacteria that helps in forming certain vitamins in the large intestine.
The bacterial population in the gut of human beings plays a vital role in the vitamin production. The microbiotia synthesize vitamin B12 and vitamin K.
These bacteria re species of bifidobacteria and lives in the gut of human being and get the food from there only.