Anemia is described as a decrease in what component of the blood?

Anemia is a condition characterized by a deficiency in the number or quality of red blood cells (RBCs), iron, or hemoglobin in the blood. Each of these components plays a crucial role in the body's ability to transport oxygen.

When there is a decrease in red blood cells, the body struggles to deliver adequate oxygen to tissues and organs. Hemoglobin is the protein within red blood cells responsible for binding oxygen; therefore, a reduction in hemoglobin can also lead to insufficient oxygenation. Iron is essential for the production of hemoglobin, as it is a critical component of this protein. Without adequate iron, the body cannot produce sufficient hemoglobin, which can subsequently result in anemia.

Thus, since anemia can stem from a decrease in any or all of these important components—red blood cells, hemoglobin, and iron—the choice 'All of the above' is accurate. Each element is interrelated, and a deficiency in one can lead to deficiencies in the others, contributing to the overall condition of anemia.