What best describes blood?

• A. Enzymes, hormones, electrolytes
• B. Plasma, red cells, white cells, platelets
• C. Nerves, neurons, glia
• D. Hemoglobin, myoglobin, collagen

Answer: (B)

Blood is a tissue made up of a liquid portion (plasma) and solid components (the formed elements). The formed elements are red blood cells, white blood cells, and platelets. Together, plasma plus these cellular elements describe the full composition of blood, which is why this option is the best fit. The other descriptions point to substances found in blood or other tissues but don’t capture blood’s complete makeup: enzymes, hormones, and electrolytes are substances present in blood; nervous tissue components are not blood; and although hemoglobin is vital inside red blood cells, myoglobin is a muscle protein and collagen is a connective tissue protein, none alone describe blood as a whole.