The following statements refer to gas carriage by the blood. Find the correct statement.

1. After leaving the lungs, each litre of blood contains about 20 ml of oxygen.

2. Haemoglobin is half saturated with oxygen when the PO₂ is about 30 mm Hg

3. As the PCO₂ rises, the affinity of haemoglobin for oxygen is increased.

4. Each litre of arterial blood contains about 50 mL of carbon dioxide

In the given diagram of the oxygen dissociation curve, under normal physiological conditions, the partial pressure of oxygen at the tissue level is represented by :

1. A

2. B

3. C

4. D

Which of the following is true about respiration?
(1)it is for energy liberation
(2)it can occur both O2 presence and its absence
(3)In humans R.B.C show anaerobic respiration
(4)All of these

Choose the wrong statement
(1)CO2 is the harmful molecule and released during catabolic reactions
(2)respiration will always require O2
(3)Breathing is a part of respiration
(4)All of the above

Which of the following is true
(1)Gills are used by most of the aquatic animals
(2)lungs are used by most of the terrestrial animals
(3)Mammals have a well developed respiratory system
(4)All of the above

How many external nostrils are present in human beings
(1)1
(2)2
(3)3
(4)None of these

Nasopharynx opens through_________ of the larynx region into the trachea.
(1)glottis
(2)gullet
(3)epiglottis
(4)All of these

Which of the following is true about epiglottis
(1)thin elastic cartilaginous flap
(2)prevent food entry into larynx
(3)Coughing occurs due to its improper movement
(4)All of these

The common passage for food and air is
(1)nasal passage
(2)nasopharynx
(3)oropharynx
(4)pharynx

Which of the following is not supported by cartilaginous rings
(1)Primary bronchioles
(2)tertiary bronchioles
(3)tracheae
(4)alveoli