Read the following statement .
a) High `H^+` concentration and higher temperature are favourable for dissociation of oxygen from oxyhaemoglobin.
b) Partial pressure of oxygen in alveoli is higher than in tissue .
c) The maximum volume of air a person can breather in after a forced expiration is vital capacity.
d) In alveoli `PCO_2` low and `PO_2` high are for dissociation of `CO_2` from carbamino haemoglobin .
How many of the above statement are true ?

Options

A. One
B. Two
C. Three
D. Four

Answer

To determine how many of the given statements are true, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** High `H^+` concentration and higher temperature are favourable for dissociation of oxygen from oxyhaemoglobin.

- **Analysis:** When the concentration of hydrogen ions (`H^+`) increases (which lowers pH), and when the temperature increases, the affinity of hemoglobin for oxygen decreases. This means that oxygen is more likely to dissociate from oxyhemoglobin under these conditions. Therefore, this statement is **true**.

### Step 2: Analyze Statement B
**Statement B:** Partial pressure of oxygen in alveoli is higher than in tissue.

- **Analysis:** In the alveoli, the partial pressure of oxygen (`PO2`) is indeed higher than in the tissues. This difference in partial pressure allows oxygen to diffuse from the alveoli into the blood and then to the tissues where it is utilized. Therefore, this statement is **true**.

### Step 3: Analyze Statement C
**Statement C:** The maximum volume of air a person can breathe in after a forced expiration is vital capacity.

- **Analysis:** Vital capacity is defined as the maximum amount of air a person can exhale after a maximum inhalation, not after a forced expiration. The volume of air that can be inhaled after a forced expiration is actually called the inspiratory capacity. Therefore, this statement is **false**.

### Step 4: Analyze Statement D
**Statement D:** In alveoli `PCO2` low and `PO2` high are for dissociation of `CO2` from carbamino haemoglobin.

- **Analysis:** In the alveoli, the partial pressure of carbon dioxide (`PCO2`) is low and the partial pressure of oxygen (`PO2`) is high. This condition facilitates the release of carbon dioxide from carbaminohemoglobin back into the alveoli for exhalation. Therefore, this statement is **true**.

### Conclusion
Now, we summarize the truth values of each statement:
- Statement A: True
- Statement B: True
- Statement C: False
- Statement D: True

**Total True Statements:** 3 out of 4 statements are true.

### Final Answer
**3 statements are true.**