Answer:
Vitamin K
Explanation:
Vitamins A, D, E and K are the fat-soluble vitamins. Vitamin K is mainly required for the synthesis of blood-clotting proteins. Microbiota, the microbes present in our bodies ensure to maintain good health by the production of some important vitamins. For example, E. coli. and other bacteria present in the intestines of human beings serve to synthesize vitamin B and vitamin K. Vitamin K is required for the production of prothrombin in liver cells. Prothrombin is converted into thrombin during blood clotting.