In human blood, which of the following components is primarily responsible for carrying oxygen from the lungs to different parts of the body?

Introduction / Context:
Efficient transport of oxygen is vital for the survival of body tissues. In humans, blood is the medium that carries oxygen from the lungs to cells. This question asks you to identify which component of blood is mainly responsible for transporting oxygen throughout the body.

Given Data / Assumptions:

• The components listed are red blood cells, white blood cells, plasma, and nerves.
• We assume normal human physiology with intact circulatory and respiratory systems.
• The focus is specifically on the transport of oxygen, not carbon dioxide or nutrients.

Concept / Approach:
Red blood cells (RBCs), or erythrocytes, contain haemoglobin, an iron containing protein that binds oxygen in the lungs and releases it in the tissues. This makes RBCs the primary oxygen carriers in the body. White blood cells (WBCs) are mainly involved in immune defense. Plasma is the liquid portion of blood that carries dissolved substances, including a small amount of oxygen, but most oxygen is bound to haemoglobin in RBCs. Nerves are not part of blood; they are components of the nervous system and conduct electrical impulses, not gases. Therefore, the correct answer must name red blood cells.

Step-by-Step Solution:
Step 1: Examine option A, red blood cells. They contain haemoglobin, which binds and transports oxygen, making them the primary carriers of oxygen in blood.Step 2: Examine option B, white blood cells. These cells protect the body from infections but do not have a major role in oxygen transport.Step 3: Examine option C, plasma. While plasma dissolves a small fraction of oxygen, most oxygen is carried by haemoglobin in RBCs, not by plasma alone.Step 4: Examine option D, nerves. Nerves are involved in transmitting signals and are not blood components, so they do not carry oxygen.Step 5: Conclude that red blood cells are the correct answer.

Verification / Alternative check:
To verify, think of clinical tests such as haemoglobin level and red blood cell count, which are important indicators of a person’s oxygen carrying capacity. Conditions like anaemia, where RBC count or haemoglobin is low, lead to fatigue because insufficient oxygen reaches tissues. There is no equivalent reference to white blood cells or nerves as primary oxygen carriers, which confirms the role of RBCs.

Why Other Options Are Wrong:
Option B is wrong because white blood cells function mainly in immunity, not in gas transport. Option C is wrong because although plasma carries nutrients, hormones, and some dissolved gases, it does not carry the majority of oxygen. Option D is wrong because nerves are structures in the nervous system and are not part of blood at all.

Common Pitfalls:
Some students may confuse the roles of different blood components or may assume that because plasma is the liquid part, it carries everything equally. It is important to remember that haemoglobin in red blood cells is specifically adapted for oxygen binding and release. Keeping the roles of RBCs, WBCs, plasma, and platelets clear in your mind will help you solve many similar questions quickly.

Final Answer:
Red blood cells.