Which type of blood cell is primarily responsible for transporting oxygen?

Erythrocytes, commonly known as red blood cells, are primarily responsible for transporting oxygen throughout the body. These cells contain hemoglobin, a specialized protein that binds to oxygen in the lungs and carries it to tissues and organs. The unique biconcave shape of erythrocytes increases their surface area, allowing for more effective oxygen uptake and release. This function is essential for maintaining the metabolic processes that sustain life, as oxygen is crucial for cellular respiration.

Leukocytes, or white blood cells, play a significant role in the immune system but are not involved in oxygen transport. Platelets are cell fragments that are vital for blood clotting and wound healing, while plasma cells are a type of white blood cell that produce antibodies and are part of the immune response. Thus, erythrocytes are the specialized cells focused on oxygen transport, making them the correct answer.