The correct answer is Severe asthma attack.

- Respiratory acidosis occurs when there is an impairment in ventilation leading to CO₂ retention, resulting in an increased partial pressure of carbon dioxide (PaCO₂) in the blood.
- This condition is primarily caused by hypoventilation or inadequate gas exchange in the lungs.

- In the setting of a severe asthma attack, bronchospasm and airway obstruction cause difficulty in effectively exhaling air, leading to air trapping and alveolar hypoventilation.
- This results in the accumulation of CO₂ and subsequent respiratory acidosis.
- In contrast, other options such as pulmonary embolism, pneumothorax, and pulmonary fibrosis can cause hypoxemia and respiratory distress but do not typically result in acute CO₂ retention leading to respiratory acidosis as the primary abnormality.
- For example, pulmonary embolism mainly causes ventilation-perfusion mismatch and hypoxemia without significant CO₂ retention.
- Similarly, pneumothorax leads to lung collapse and impaired oxygenation but does not usually cause CO₂ retention unless ventilation is severely compromised.
- Pulmonary fibrosis leads to a restrictive lung pattern and impaired oxygen diffusion but generally does not cause acute respiratory acidosis.

Therefore, the most common clinical condition linked to the development of respiratory acidosis among the options given is a severe asthma attack.

Reference: Harrison's Principles of Internal Medicine, 20th Edition, Respiratory System / Acid-Base Disorders, Chapter 333 / Page 2865