Oxygen is mainly transported as……… .

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of Oxygen**: Oxygen is essential for respiration, which is the process through which cells obtain energy. Every cell in the body requires oxygen to function properly.

2. **Breathing and Gas Exchange**: Breathing involves the exchange of gases, specifically oxygen and carbon dioxide, between the body and the atmosphere. This exchange occurs in the lungs.

3. **Transport Mechanism of Oxygen**: Once oxygen is inhaled, it needs to be transported to various cells in the body. The primary method of oxygen transport in the blood is through red blood cells (RBCs).

4. **Percentage of Oxygen Transport**: Approximately 97% of the oxygen in the blood is carried by red blood cells, while the remaining 3% is dissolved in the plasma (the liquid component of blood).

5. **Role of Hemoglobin**: Within the red blood cells, there is a pigment called hemoglobin, which is iron-containing and gives blood its red color. Hemoglobin has the ability to bind with oxygen.

6. **Formation of Oxyhemoglobin**: Each hemoglobin molecule can bind with up to four molecules of oxygen, forming a compound known as oxyhemoglobin. This compound is how oxygen is transported through the bloodstream to tissues and organs.

7. **Conclusion**: Therefore, oxygen is mainly transported in the blood by red blood cells in the form of oxyhemoglobin.

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