B. Write down the major functions of blood circulatory system.

The circulatory system is responsible for many functions that we perform.

it transports oxygen and nutrient throughout the human body.

The blood carries useful substances to the cells and takes away the waste products of the cells, which include urea, carbon dioxide and other metabolic wastes.

blood carries white blood cells and platelets, which help protect the body by clotting wounds and fighting off pathogens.

Hope this helps (●'◡'●)

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.