Which of the following situations would result in the greatest degree of ${\mathrm{O}}_2$ saturation for haemoglobin, assuming ${\mathrm{PO}}_2$ remains constant-

1.  Increased ${\mathrm{H}}^{+}$ levels, decreased temperature.

2.  Increased ${\mathrm{CO}}_2$ levels, increased acidity.

3.  Decreased ${\mathrm{CO}}_2$ levels, decreased acidity.

4.  Increased ${\mathrm{CO}}_2$ levels, increased temperature.

Consider the characters of a respiratory control center in humans:
I. It is located in pons
II. It moderates the functions of respiratory rhythm center
III. Its absence results in an increase in depth of respiration

The respiratory control center is:

1. Pneumotaxic center

2. Apneustic center

3. Chemosensitive zone

4. Dorsal group

According to Bohr's effect

1.  Hemoglobin oxygen binding affinity is inversely related to acidity.

2.  Hemoglobin oxygen binding affinity is inversely related to concentration of ${\mathrm{CO}}_2$.

3.  Hemoglobin oxygen binding affinity is directly related to acidity.

4.  Both 1 and 2.

Asthma may be attributed to?

1. allergic reaction of the mast cells in the lungs
2. inflammation of the trachea
3. accumulation of fluid in the lungs
4. bacterial infection of the lungs

The figure given below shows a small part of the human lung where exchange of gases takes place. In which one of the options given below, the one part A, B, C or D is correctly identified along with its function?

   

1.	A – Alveolar cavity – main site of exchange of respiratory gases
2.	D – Capillary wall – exchange of O2 and CO2 takes place here
3.	B – Red blood cell –  transport of CO2 mainly.
4.	C – Arterial capillary – passes oxygen to tissues

Listed below are four respiratory capacities (1-4) and four jumbled respiratory volumes of a normal human adult. 

Which one of the following is the correct matching of two capacities and volumes?

1. (a) 2500 mL, (d) 4500 mL

2. (c) 1200 mL, (a) 2500 mL

3. (b) 4500 mL, (c) 2500 mL

4. (d) 4500 mL, (b) 3500 mL