Which statement best describes the function of fibrinogen?

A) It provides the nutrients needed to replicate erythrocytes.
B) It transports lipids, playing a role in clotting and defending the body against foreign substances.
C) It aids in the structural form of the erythrocyte.
D) It is the key substance in the formation of blood clots.
E) It primarily affects the movement of fluid into capillaries by creating an osmotic gradient.