Blood is fluid connective tissues. The main function of fluid connective tissue are binding, protecting and connecting together different organs of the body. Blood has these qualities that's why we called them connective tissue.
Let us see how they fullfil these qualities :
Binding : (a) Blood : it carries oxygen, carbon dioxide, digested food, hormones and waste product (urea) from one part to another.
Protecting :(a) Blood : protect the body from diseases with the help of WBC(white blood cells).
Connecting different organs :(a) Blood : it connects together each and every part of the body. As blood is necessary for whole body.