Low oxygen tension in the blood causes

Options

A. Coughing
B. Hiccups
C. Sneezing
D. Yawning.

Answer

### Step-by-Step Solution:

1. **Understanding Low Oxygen Tension**: Low oxygen tension in the blood refers to a decreased level of oxygen available in the bloodstream. This condition can occur due to various reasons such as high altitude, respiratory diseases, or other health issues.

2. **Body's Response to Low Oxygen**: When the body detects low oxygen levels, particularly in the brain, it initiates a response to increase oxygen intake. The brain monitors oxygen levels and triggers various physiological responses to correct the deficiency.

3. **Yawning as a Response**: One of the primary responses to low oxygen tension is yawning. Yawning is a reflex action that involves opening the mouth wide and taking a deep inhalation. This action allows for a significant intake of air, which increases the amount of oxygen entering the lungs.

4. **Mechanism of Yawning**: During yawning, the mouth is widely opened, and a large volume of air is inhaled. This helps to compensate for the decreased oxygen concentration in the blood by increasing the oxygen levels in the lungs, which then get transported to the bloodstream.

5. **Conclusion**: Therefore, the correct answer to the question "Low oxygen tension in the blood causes" is **yawning**. This physiological response helps to restore adequate oxygen levels in the body.