What is the primary component of blood plasma?

• A. Solutes
• B. Water
• C. Platelets
• D. Red blood cells

Answer: (B)

Blood plasma is the liquid portion of blood, the medium that carries everything dissolved or suspended in it. The main component is water, making up most of plasma by volume. Water serves as the solvent for electrolytes, nutrients, hormones, gases, and waste, and it helps maintain the volume and pressure of blood. The other constituents—solutes that are dissolved substances, plasma proteins, and various small molecules—are present, but they do not comprise as much of plasma as water. Platelets and red blood cells are formed elements suspended in plasma, not part of the plasma itself. So, water is the best answer.