People who have migrated from the planes to an area adjoining Rohtang pass about six months back

Options

A. have more RBCs and their haemoglobin
has a lower binding affinity to `O_(2)`.
B. are not physically fit to play games like
football
C. suffar from altitude sickness with symptoms like nausea, fatigue , etc .
D. have the usual RBC count but their haemoglobin has very high binding affinity

Answer

**Step-by-Step Solution:**

1. **Understanding the Context:** The question refers to people who have migrated from the plains to a high-altitude area near Rohtang Pass about six months ago. At high altitudes, the oxygen levels are lower than at sea level.

2. **Identifying Initial Symptoms:** When individuals first arrive at high altitudes, they often experience altitude sickness, which includes symptoms like nausea, fatigue, and heart palpitations. However, the question specifies that these individuals have been living there for six months, which suggests they have had time to acclimatize.

3. **Acclimatization Process:** Acclimatization is the process by which the body adjusts to lower oxygen levels. This includes physiological changes such as:
- Increased production of red blood cells (RBCs) to enhance oxygen transport.
- Changes in hemoglobin binding affinity, which may decrease to allow more oxygen to be released to the tissues.
- Increased breathing rate to take in more oxygen.

4. **Evaluating the Options:**
- **Option A:** "Have more RBC and their hemoglobin has lower binding affinity to O2." This aligns with the physiological adaptations that occur after acclimatization, making it a likely correct answer.
- **Option B:** "Are not physically fit to play games like football." This is incorrect as acclimatization generally improves physical fitness.
- **Option C:** "Suffer from altitude sickness with symptoms like nausea and fatigue." This is incorrect since they have been living there for six months and would have acclimatized.
- **Option D:** "Have usual RBC count but the hemoglobin is very high in binding affinity." This is incorrect because acclimatization typically leads to an increase in RBC count and a decrease in hemoglobin's binding affinity.

5. **Conclusion:** After evaluating all options, the correct answer is **Option A**: "They have more RBC and their hemoglobin has lower binding affinity to O2."

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