Given below is a list of different steps (i-vi) involved in respiration.
(i) Utilisation of `O_(2)` by the cells for cataolic reactions.
(ii) Transport of gases by the blood.
(iii) Pulmonary ventilation by which atmospheric air is drawn in and `CO_(2)` is released out.
(iv) Release of resultant `CO_(2)`.
(v) Diffusion of `O_(2)` and `CO_(2)` between blood and tissues.
(vi) Diffusion of gases (`O_(2)` and `CO_(2)`) across alveolar tissues.
Select an option which has correct sequence of all the steps.

Options

A. a) (iii),(vi),(ii),(v),(i),(iv)
B. b) (iii),(vi),(i),(v),(ii),(iv)
C. c) (iv),(ii),(v),(iii),(i),(vi)
D. d) (iv),(vi),(ii),(v),(i),(iii)

Answer

To solve the question regarding the correct sequence of steps involved in respiration, we need to analyze the steps provided and arrange them logically based on the physiological process of respiration.

### Step-by-Step Solution:

1. **Identify the Steps**:
- (i) Utilization of O₂ by the cells for catabolic reactions.
- (ii) Transport of gases by the blood.
- (iii) Pulmonary ventilation by which atmospheric air is drawn in and CO₂ is released out.
- (iv) Release of resultant CO₂.
- (v) Diffusion of O₂ and CO₂ between blood and tissues.
- (vi) Diffusion of gases (O₂ and CO₂) across alveolar tissues.

2. **Determine the Order of Events**:
- **Step 1**: **Pulmonary ventilation (iii)** occurs first, as it involves the intake of atmospheric air into the lungs.
- **Step 2**: **Diffusion of gases across alveolar tissues (vi)** happens next, where O₂ enters the blood and CO₂ is released from the blood into the alveoli.
- **Step 3**: **Transport of gases by the blood (ii)** follows, where O₂ is transported to tissues and CO₂ is transported back to the lungs.
- **Step 4**: **Diffusion of O₂ and CO₂ between blood and tissues (v)** occurs as O₂ moves from the blood into the tissues and CO₂ moves from the tissues into the blood.
- **Step 5**: **Utilization of O₂ by the cells for catabolic reactions (i)** takes place in the tissues, where O₂ is used for metabolism.
- **Step 6**: **Release of resultant CO₂ (iv)** is the final step, where CO₂ produced from cellular respiration is released into the blood to be transported back to the lungs.

3. **Final Sequence**:
- The correct sequence of steps is:
- (iii) Pulmonary ventilation
- (vi) Diffusion of gases across alveolar tissues
- (ii) Transport of gases by the blood
- (v) Diffusion of O₂ and CO₂ between blood and tissues
- (i) Utilization of O₂ by the cells
- (iv) Release of resultant CO₂

### Conclusion:
The correct order of the steps is: **(iii), (vi), (ii), (v), (i), (iv)**.