Respiratory System Transport Of Gases Part 1

People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 meters have around 8 million. This is because at high altitudes:

1.	people get pollution-free air to breathe and more oxygen is available
2.	atmospheric O2 level is less and hence more RBCs are needed to absorb the required amount of O2 to survive
3.	there is more UV radiation which enhances RBC production
4.	people eat more nutritive food, therefore more RBCs are formed

A large proportion of oxygen is left unused in the human blood even after its uptake by body tissues. This O₂:

1. raises the P_co2 blood to 75 mm of Hg

2. is enough to keep oxyhaemoglobin

3. helps in releasing more O₂ to the epithelial tissues

4. acts as a reserve during muscular exercise

Which of the following factors are favourable for the formation of oxyhaemoglobin in alveoli?
1. High and Lesser concentration
2. Low and High concentration
3. Low and High temperature
4. High and High