At higher altitudes, a man suffers much from

Options

A. Cold
B. Oxygen deficiency
C. Higher atmospheric pressure
D. Ultraviolet radiations.

Answer

**Step-by-Step Solution:**

1. **Understanding Atmospheric Conditions at Sea Level:**
- At sea level, the atmospheric concentration of oxygen is about 21%, and the barometric pressure is approximately 760 mmHg. This means that there is a sufficient amount of oxygen available for breathing.

2. **Conditions at Higher Altitudes:**
- As altitude increases, the barometric pressure decreases. Although the percentage of oxygen in the atmosphere remains around 21%, the number of oxygen molecules per breath decreases due to lower pressure.

3. **Impact on Breathing:**
- At high altitudes, each breath contains significantly less oxygen compared to sea level. This can lead to a situation where the body does not receive enough oxygen to function properly.

4. **Physiological Response:**
- To compensate for the reduced oxygen availability, a person will breathe faster and the heart will beat faster. This is an attempt to increase the oxygen levels in the blood, but even with these compensatory mechanisms, the oxygen levels do not reach those found at sea level.

5. **Consequences of Oxygen Deficiency:**
- If a person does not acclimatize to high altitudes, they may experience symptoms related to oxygen deficiency. This can lead to serious conditions such as fluid buildup in the lungs (pulmonary edema) and in the brain (cerebral edema).

6. **Conclusion:**
- The primary reason a person suffers at higher altitudes is due to oxygen deficiency caused by lower atmospheric pressure and reduced availability of oxygen per breath.

**Final Answer:**
At higher altitudes, a man suffers much from oxygen deficiency.

---