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

Hint: Blood is a fluid connective tissue which is red in colour and functions as a medium to transport necessary substances like oxygen and nutrients to the cells.

Complete Answer:
Before we find the correct answer, let us first know the various components of blood. The various components of blood are,
(I) Plasma
(II) Erythrocytes or Red blood cells
(III) Leukocytes or White blood cells
(IV) Platelets

Option A: Plasma is a viscous fluid which is straw coloured and fluid part of the blood. It constitutes 55% of the blood. The constituents of plasma are,
Water - 90-92%
Proteins - 6-8%
There are various types of plasma proteins, they are,
1. Albumin - It helps in transport of substances like fatty acids, bilirubin, ions, metals, etc.
2. Globulin - It is produced in the liver and has a role in liver function, fighting infection and blood clotting.
3. Fibrinogen - It has a role in clotting of blood.
4. Electrolytes - Various electrolytes like Sodium, Potassium, etc.

Option B: Serum is basically plasma but without clotting factors. But this is not known as the fluid component of blood. Therefore, this is the incorrect option.

Option C: Plasma protein is basically proteins present in the plasma. They are not fluid components and therefore, this is the incorrect option.

Hence the correct answer is option A.

Note: Plasma makes up to 55% of the blood and when it is separated from blood it is yellow in colour. The other components of blood are RBC (45%) and WBC (0.7%).