**Core Concept:**
In the context of cardiopulmonary arrest, airway management is crucial to ensure oxygenation and ventilation, which are essential for maintaining blood oxygen levels and preventing multi-organ failure. The primary goal is to establish an unobstructed airway for effective ventilation.

**Why the Correct Answer is Right:**
The correct answer is **C. Oral route** because, in a patient of cardiopulmonary arrest, the goal is to quickly establish an unobstructed airway for ventilation. In the oral route, we can perform direct laryngoscopy and intubation, which is generally considered the gold standard for securing an airway during cardiopulmonary arrest. This approach allows for optimal visualization of the glottis and trachea, facilitating the insertion of an endotracheal tube.

**Why Each Wrong Option is Incorrect:**

A. **Nasopharyngeal airway (NPA):** Although NPA can be used as a temporary airway, it is not suitable for cardiopulmonary arrest because it provides inadequate ventilation and is prone to obstruction due to secretions or vomiting.
B. **Nasal route:** Nasal intubation is difficult and less efficient than oral intubation, leading to inadequate ventilation and poor oxygenation during a critical event like cardiopulmonary arrest.
D. **Subglottic suctioning:** Subglottic suctioning is an attempt to clear secretions from the airway, but it does not secure the airway, which is essential in a patient with cardiopulmonary arrest.

**Clinical Pearl:**
In cardiopulmonary arrest, the airway should be secured promptly to ensure adequate oxygenation and ventilation, preventing secondary brain injury and multi-organ failure. The oral route allows for direct laryngoscopy and intubation, which is crucial in this critical setting.

**Correct Answer:** C. Oral route