Q. ____ is a straw coloured, viscous fluid constituting nearly 55 per cent of the blood:
Answer: Plasma
Notes: Plasma is a straw coloured, viscous fluid constituting nearly 55 per cent of the blood. 90-92 per cent of plasma is water and proteins contribute 6-8 per cent of it. Fibrinogen, globulins and albumins are the major proteins. Fibrinogens are needed for clotting or coagulation of blood; while, globulins primarily are involved in defense.