Which of the following statements about blood plasma is true?

Introduction / Context:
Blood plasma is the liquid portion of blood that suspends cells and carries nutrients, hormones, and waste products. Understanding its composition is important for topics such as circulation, immunity, and clinical laboratory tests. This question asks you to identify the correct statement about plasma from among several partly true or completely incorrect descriptions.

Given Data / Assumptions:

Whole blood contains red blood cells, white blood cells, platelets, and plasma.
Plasma is the fluid fraction left after cells are removed.
Serum is related to plasma but is not identical.

Concept / Approach:
Plasma is a straw colored or faint yellow liquid that accounts for a little more than half of total blood volume. It is mostly water, typically around 90 to 92 percent, with the remainder made up of dissolved proteins, salts, nutrients, wastes, and other substances. The main plasma proteins include albumin, globulins, and clotting proteins such as fibrinogen. Hemoglobin is not a plasma protein; it is found inside red blood cells. Serum is plasma from which clotting factors have been removed after clot formation, so it is not correct to say that plasma is serum without clotting proteins. Plasma is certainly not free of proteins, because its proteins are vital for osmotic balance, transport, and clotting.

Step-by-Step Solution:
Step 1: Recall that plasma is the liquid portion of blood and appears pale yellow in color. Step 2: Remember that plasma is about 90 percent water, with the rest composed of proteins and solutes. Step 3: Review the options and identify the one that correctly states both the color and high water content of plasma. Step 4: Confirm that the other statements either misidentify the major protein or are wrong about the relationship between plasma and serum.

Verification / Alternative check:
Laboratory manuals describe the composition of plasma and serum in detail. They emphasize that albumin is the most abundant plasma protein and that serum is plasma with clotting factors removed. Visual observation also shows that plasma is pale yellow and fluid, consistent with high water content. These facts support the statement that plasma is a faint yellow fluid that is about 90 percent water.

Why Other Options Are Wrong:
Main protein is hemoglobin: Hemoglobin is located inside red blood cells, not dissolved as the main protein in plasma.
Plasma is serum minus clotting proteins: The opposite is true; serum is plasma minus clotting proteins after clotting has occurred.
Plasma contains no proteins: Plasma actually contains important proteins such as albumin, globulins, and fibrinogen, so this statement is clearly incorrect.

Common Pitfalls:
A common confusion is between plasma and serum, especially regarding clotting proteins. Another pitfall is to think of hemoglobin as a free plasma protein because it is associated with blood, when in reality it is contained within red blood cells. Keeping clear definitions for whole blood, plasma, and serum helps avoid mistakes in questions like this one.

Final Answer:
The true statement is that blood plasma is a faint yellow fluid that is about 90 percent water.