Final answer:
Iron deficiency anemia is characterized by decreased red blood cell count, hemoglobin levels, and oxygen carrying capacity.
Step-by-step explanation:
The correct answer is 4) all of the above. Iron deficiency anemia is characterized by decreased red blood cell count, hemoglobin levels, and oxygen carrying capacity. This condition occurs when there is an insufficient amount of iron present in the body to produce enough hemoglobin, the protein responsible for carrying oxygen in red blood cells.