Among common plasma proteins, which is present in the lowest concentration?

• A. Albumin
• B. Immunoglobulins
• C. Fibrinogen
• D. Transferrin

Answer: (C)

The question tests how the body prioritizes different plasma proteins based on their functions, which drives their normal concentrations. Albumin is the most abundant protein in plasma and is essential for maintaining oncotic pressure and serving as a carrier for many substances. Immunoglobulins (antibodies) are also present in substantial amounts to provide immune defense. Transferrin, which transports iron, is present but at a relatively modest level. Fibrinogen, a coagulation factor that becomes fibrin during clot formation, is kept at a lower baseline concentration in circulating plasma.

Given these roles, fibrinogen is present in the lowest concentration among the listed proteins.