Which of the following is functional for protection against the environmental abiotic factor of temperature or for thermoregulation of the living body during winter or summer?

At sea level,the blood of individuals contains approximately $5$ million red blood cells per cubic millimeter. However,individuals living at an altitude of $5400$ meters have $8$ million red blood cells per cubic millimeter. Why does this increase occur?

Persons living at high altitude will have

If a man from the sea coast goes to the Everest peak,then:

Which of the following two changes occur in humans when they move to high altitudes (above $3,500 \ m$)?
$(1)$ Increase in red blood cell size
$(2)$ Increase in red blood cell production
$(3)$ Increase in breathing rate
$(4)$ Increase in thrombocyte count

Respiration is the physiological process in which