What was the question for this implicit rationale, and corresponding answer?
The important part for answering this question is: It makes up about 55 % of the body's total blood volume.
The answer: 55 %
The question: Blood plasma is a yellowish coloured liquid component of blood that normally holds the blood cells in whole blood in suspension; this makes plasma the extracellular matrix of blood cells. It makes up about 55 % of the body's total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside cells). It is mostly water (up to 95 % by volume), and contains dissolved proteins (6 -- 8 %) (i.e. -- serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na, Ca, Mg, HCO, Cl, etc.), hormones, carbon dioxide (plasma being the main medium for excretory product transportation) and oxygen. Plasma also serves as the protein reserve of the human body. It plays a vital role in an intravascular osmotic effect that keeps electrolytes in balanced form and protects the body from infection and other blood disorders.

Answer this question: what percentage of blood is composed of plasma?