**Core Concept:**
The question is testing the understanding of a patient presenting with postoperative complications following squint surgery. The symptoms described are signs of a potentially life-threatening complication called Difficult Airway Syndrome (DAS) or Postoperative Airway Obstruction (PAO). This condition occurs due to accumulation of secretions and blood in the larynx and trachea, leading to compromised airway patency and subsequent hypoxia, hypercapnia, acidosis, and hyperpyrexia.

**Why the Correct Answer is Right:**
The correct answer, **D. Neostigmine**, is a cholinesterase inhibitor that works by increasing the concentration of acetylcholine at the neuromuscular junction. In the context of DAS, neostigmine helps to counteract the effects of paralysis induced by the muscle relaxants used during surgery, thereby improving airway patency and ventilation.

**Why Each Wrong Option is Incorrect:**
A. **Atropine**: While atropine is another anticholinergic drug, it has a lesser affinity for the muscarinic receptors compared to neostigmine. As a result, atropine is not as effective in reversing the effects of muscle relaxants and is not the first choice for managing DAS.

B. **Nebulized salbutamol**: Salbutamol is a beta-2 agonist used in asthma management, not related to the management of DAS.

C. **Nebulized salbutamol with nebulized atropine**: This combination does not address the primary issue of airway obstruction caused by DAS, making it an incorrect choice for management.

**Clinical Pearl / High-Yield Fact:**
Postoperative respiratory complications like DAS are rare, but critical, and immediate intervention is crucial to prevent worsening of the condition and subsequent respiratory failure.

**Correct Answer Explanation:**
In the context of DAS, neostigmine is the first-choice agent as it has a higher affinity for muscarinic receptors and is more effective in reversing the effects of muscle relaxants. By doing so, neostigmine can improve airway patency and ventilation, which is essential in managing the life-threatening condition of DAS.