What is plasma?

Plasma is indeed a pale yellow or gray-yellow fluid component of blood, primarily consisting of water, electrolytes, proteins, hormones, and waste products. It makes up about 55% of total blood volume and serves multiple vital functions in the body. One of its key roles is to transport nutrients, hormones, and proteins to the parts of the body that need them while also assisting in the removal of waste products.

In contrast to the other options, which describe different components or aspects of the body's physiology, the description of plasma accurately captures its composition and function in the circulatory system. For example, a type of blood cell responsible for immunity refers specifically to white blood cells, which play a distinct role separate from the fluid component of blood. Similarly, proteins involved in muscle contraction are distinct from plasma proteins; these are specialized proteins like actin and myosin. The mention of carbon dioxide also pertains to gases carried in the bloodstream, typically bound to hemoglobin or dissolved as bicarbonate, rather than describing a fluid component like plasma. Therefore, the choice that identifies plasma as a pale yellow protein found in the body is the correct characterization of this essential bodily fluid.