Fluid medium of blood is called as A. PlasmaB. Serum C. Plasma Protein D. None of the above

The fluid medium of blood is called A. Plasma.

Explanation:
Plasma is the yellowish liquid component of blood that holds the blood cells in suspension. It is composed of water, electrolytes, nutrients, hormones, and waste products. Plasma constitutes about 55% of total blood volume.
Serum is the liquid that remains after blood has clotted and does not contain clotting factors like fibrinogen. It is essentially plasma without clotting proteins.
Plasma Protein refers to the proteins found in plasma, such as albumin, globulins, and fibrinogen, but it does not denote the fluid medium itself.
None of the above is incorrect, as plasma is indeed the fluid medium of blood.
Thus, the correct answer is A. Plasma.