Fibrinogen is not a formed element of blood. It's a chemical component in the plasma. The formed elements of blood are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
I do believe that the answer is erythrocytes. Erythrocytes are the formed element in blood that transport oxygen and carbon dioxide.
gamma globulin
An extract of human blood that contains antibodies
leukocytes
Thrombocytes are the smallest formed elements in the blood. In my Medical Terminology book, it says "The smallet formed elements found in blood are platelets. Although they are sometimes called thrombocytes, they are not true cells, as the term erroneously suggests, but merely fragments of cells."
Alpha globulin
Basophils are one of the formed elements of blood. Basophils are the least common type of white blood cell. The formed elements of blood are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
Gamma Globulin
with blood tranfusion of plalets
low immunity
Red Blood Cell
Normal range in blood is 2.0 - 3.5