The trachea divides into a right and a left primary bronchi at the level of:
1. 3^rd thoracic vertebra
2. 5^th thoracic vertebra
3. 7^th thoracic vertebra
4. 12^th thoracic vertebra

Incomplete cartilaginous rings are seen in the walls of all the following except:

The peripheral chemoreceptors for regulation of respiration are located:
1. adjacent to the rhythm center
2. near arch of aorta and carotid artery
3. in the walls of trachea
4. in the walls of the alveoli

When carbon dioxide combines with haemoglobin in blood, it forms:
1. Carboxyhemoglobin
2. Carbaminohemoglobin
3. Methemoglobin
4. Oxidized hemoglobin

Which of the following has the highest affinity for oxygen?
1. HbS
2. HbA
3. HbF
4. Methemoglobin

Which of the given three layers in the respiratory membrane is/are one-celled thick?

Which occupational lung disorder can lead to cancer of lung?
1. Silicosis
2. Byssinosis
3. Bagassosis
4. Asbestosis

It is necessary that lungs must be present in anatomically air-tight chamber because: 

The respiratory diffusion membrane is made of all the following layers except:

Consider the following statements:

1. Both I and II are correct and II explains I
2. Both I and II are correct and I explains II
3. Both I and II are correct but II does not explain I
4. Both I and II are incorrect