Give the reason for low concentration of oxygen in the blood and tissues of people living at high altitude

Low atmospheric pressure

The correct answer is Option (3) → Low atmospheric pressure
The low concentration of oxygen in the blood and tissues of people living at high altitude is due to Low atmospheric pressure.

Reasoning:
At high altitudes, the atmospheric pressure decreases, which means the partial pressure of oxygen also decreases. Because of this, less oxygen enters the lungs and diffuses into the blood, leading to lower oxygen levels in body tissues.

• Low temperature is not the main cause of reduced oxygen availability.

• High atmospheric pressure is incorrect because pressure actually falls with altitude.

• “Both low temperature and high pressure” is wrong since high pressure does not occur at high altitude.

Therefore, the correct answer is: Low atmospheric pressure.